Carbon

Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table.

History and Discovery

The discovery of carbon dates to prehistoric times and was used by ancient human civilizations as in the form of charcoal and coal. Diamonds were discovered in China in around 2500BCE. The name carbon has been derived from the word carbo (Latin for coal and charcoal). Carbon was discovered as a novel element by 1722 by Antoine Ferchault de Réaumur, who proposed that this novel element can be used to transform iron into steel. Later in 1786, A. Vandermonde, Claude Louis Berthollet, and Gaspard Monge confirmed that graphite was a form of carbon in the same way as diamond (discovered earlier in 1772) [1].

Carbon

Periodic Table ClassificationGroup 14
Period 3
State at 20CSolid
ColorBlack
Electron Configuration[He] 2s2 2p2
Electron Number6
Proton Number6
Electron Shell2, 4
Density2.26 g.cm-3 at 20°C
Atomic number6
Atomic Mass12.01 g.mol -1
Electronegativity according to Pauling2.55

Occurrence

Carbon is characterized as the 4th most abundant element in the universe and the 15th most abundant element in the Earth’s crust. Biologically, carbon holds a significant position and is part of all living systems. In humans, carbon makes about 18.5% of body mass and is the second most abundant element in the body [2]. Atomic form of carbon is very short lived and readily stabilizes in multi-atomic configurations. Carbon exists in various forms, termed as allotropes (variation in bonding of carbon atoms due to its valency). The common allotropes of carbon include diamond, graphite, amorphous carbon (charcoal and carbon black) and nanoforms of carbon including graphene and fullerenes [3]. Carbon is major hydrocarbons present in fossil fuels including coal, natural gas, and crude oil. Carbon is also present in stars and sun and in the atmosphere of many planets. Natural reserves of diamond are present in Canada, Congo, Russia and South Africa.

Physical Properties

The different allotropic forms of carbon have different physical properties. Graphite is black, opaque and extremely soft, while crystal is highly transparent and is the hardest natural element. The electrical conductivity of graphite is very good as compared to diamond, which is an outstanding electrical insulator [4]. Carbon and its allotropes have the highest thermal conductivities as compared to all elements. Elemental carbon is insoluble in water, organic solvents and acids and bases. Graphite is the most thermodynamically stable allotrope of carbon at standard temperature and pressure. All allotropes of carbon are solid under standard conditions. Carbon and its allotropes are resistant to melting at atmospheric pressure and remain solid at considerably high temperature. Mostly, the oxidation state of carbon is +4 (in inorganic compounds) and +2 in organic compounds. Carbon has the ability to sublime (ability to transform directly from solid to gas state at high temperature) and have the highest sublimation point. The density of graphite and diamond are 2.25 g/cm³ and 3.51 g/cm³, respectively [5].  

Chemical Properties

Carbon is quite reactive and forms about one million different compounds, and there is a significant increase in their number each year. Graphite is more reactive than diamond. Carbon is quite resistant to oxidation by strongest oxidizers at normal conditions. At higher temperatures, however, carbon forms carbon oxides by reacting with oxygen, which is an exothermic reaction. There are three oxides of carbons: carbon suboxide (C3O2), carbon dioxide (CO2) and carbon monoxide (CO). Carbon can form carbides by reacting with certain metals at high temperatures, such as tungsten carbide. Fluorine is the only halogen gas that can react with carbon in elemental form [5].

Significance and Uses

  • Graphite is widely used in refractory applications and making greasy lubricants [6].
  • Graphite is used in making furnace lining, carbon brushes in motors.
  • Activated carbon or charcoal is used in making filters for respirators and kitchen hoods.
  • Diamond is used in making drills and cutter for cutting rocks and other hard material, due to its immense strength and durability.
  • Carbon fiber is used in making fishing rods, tennis rackets, airplanes as it is extraordinarily strong and light weight.
  • Carbon has revolutionized nanotechnology by the discovery of carbon nanotubes, that are widely used in electronic industry.
  • Carbon is widely used in carbonated and fuzzy drinks.
  • It is used in various metallurgy processes.
  • Carbon black is used in making pigments and inks.
  • Carbon dioxide is used in fire extinguishers and as dry ice.

Health Hazards

The increased atmospheric concentration of carbon has become a major health and environmental challenge. And carbon oxides (CO2 and CO) are characterized as the major contributors of Global warming. About 2 decades ago, the natural concentration of CO2 in the Earth’s atmosphere was around 280 ppm and has increased to 390 ppm (in 2013) due to human activities, such as burning of fossil fuels with oxygen. The natural concentration of atmospheric carbon dioxide controls a certain phenomenon known as greenhouse effects, which allows visible light to escape the Earth’s atmosphere but prevents some infrared rays from escaping. This leads to an increase in the atmospheric heat and temperature, which naturally helps in sustaining the life on Earth. But a considerable increase in the greenhouse, due to a anthropogenic emission of CO2 have become a global challenge and is bringing an unprecedented climatic change that can affect the natural balance of life [7]. Carbon is characterized as low toxicity metal. Inhalation of carbon black can lead to damage of lungs, but it is an occupational hazard. Certain compounds of carbon are also toxic, including cyanide and carbon monoxide.

 Isotopes of Carbon

There are three naturally occurring isotopes of carbon, 12C and 13C (stable isotopes), while 14C is a radionuclide, that have a half-life of about 5,730 years. Carbon-12 is the most abundant, with a natural abundance of 98.93. Carbon-14 is only present in trace amount on Earth and is mostly present in the atmosphere, where it is formed from the interaction of cosmic rays and nitrogen [8].

 

REFERENCES

[1]. Giolitti, Federico (1914). The Cementation of Iron and Steel. McGraw-Hill Book Company, inc.

[2]. Reece, Jane B. (31 October 2013). Campbell Biology (10 ed.). Pearson. ISBN 9780321775658.

[3]. “World of Carbon – Interactive Nano-visulisation in Science & Engineering Education (IN-VSEE)”. Archived from the original on 2001-05-31. Retrieved 2008-10-09.

[4]. Deprez, N.; McLachan, D. S. (1988). “The analysis of the electrical conductivity of graphite conductivity of graphite powders during compaction”. Journal of Physics D: Applied Physics. 21 (1): 101–107. Bibcode:1988JPhD…21..101D. doi:10.1088/0022-3727/21/1/015.

[5]. http://www.elementalmatter.info/carbon-properties.htm

[6]. https://mineralseducationcoalition.org/minerals-database/graphite/

[7]. http://www.rsc.org/periodic-table/element/6/carbon

[8]. “Carbon – Naturally occurring isotopes”. WebElements Periodic Table. Archived from the original on 2008-09-08. Retrieved 2008-10-09.

Mercury

Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum

Discovery and History

Mercury can be rightly considered as one of the elements with most ancient existence, and its discovery dates back to around 1500 B.C [1]. Initially, it was referred to as the water-silver or the liquid -silver (originated from the Greek term hydro-argyros used by Aristotle) and later Romans changed its name to Hydragyrum. In the 6th century, alchemists changed its name after the fast-moving Roman god, Mercury, with the symbol Hg (from its initial name Hydro-argyros). Mercury was greatly popular, especially in Chinese traditional medicine, due to its unique solid-liquid nature [2]. The metallic properties of mercury were discovered by Adam Braun and Mikhail Lomonosov (1759), who successfully froze a mercury thermometer.

Mercury

Periodic Table ClassificationGroup 12
Period 6
State at 20CLiquid
ColorSilvery
Electron Configuration[Xe] 4f14 5d10 6s2
Electron Number80
Proton Number80
Electron Shell2, 8, 18, 32, 18, 2
Density13.55 g.cm-3 at 20°C
Atomic number80
Atomic Mass200.59 g.mol -1
Electronegativity according to Pauling2.00

Occurrence

The occurrence of mercury is not very common. It is present in crust of the Earth on an average of 0.08 gram, making 0.003 ounce per ton of the rock. Mercury is rarely present in free, pure form and its principally present in the form of the red sulfide, termed as cinnabar (HgS). Naturally, mercury is present near hot springs and volcanoes in isolated drops or in larger fluid masses. Eruption of volcanoes can lead to 4-6 times increase in the atmospheric presence of volcanoes [3]. Around 2/3rd of supply of mercury in the world comes from China, and Chile and Kyrgyzstan make up the rest [4]. Mercury is often obtained as a by-product during the process of gold mining. Some other natural alloys of mercury have also been found, including potarite (with palladium) gold amalgam and moschellandsbergite (with silver), but these are extremely rare.

Physical characteristics

Mercury is a silver-white dense metal with a mirror like appearance. And have the unique characteristic of being liquid at room temperature. Mercury have boiling and melting points of 356.9 C and -38.87, respectively. It has atomic number of 80 and a molecular weight of 200.59 and belong to the Group 12 (Zinc group, II b) of the periodic table [2].

Chemical characteristics

Mercury is highly poisonous. It is generally stable in dry environment but exposure to water lead to the production of gray oxide coating on its surface. It has a low solubility for gases as compared to water. Mercury can vaporize and can stay in the atmosphere for many months.

Salts of Mercury

Various salts of mercury are present that have distinct characteristics and significances. These include mercury (I) chloride (used in medicine), Mercury (II) chloride (a very corrosive and poisonous substance);); Mercury (II) oxide (main oxide of mercury); Mercury fulminate (a detonator used in explosives widely; Mercury (II) selenide; Mercury (II) sulfide (found naturally as the ore cinnabar which is widely used paint pigment); Mercury (II) telluride, and Mercury zinc telluride (used in semiconductors) [2].

Significance and Uses

Despites its toxicity, mercury have found wide usage in variety of industries. Some of the main uses of mercury are described below:

  • Good electrical conductivity [5]

Used in making electrical switches

  • Low thermal conductivity with high thermal neutron capture [5]

Used as shield and coolant in nuclear reactors

  • Health care and dentistry [5]

Main use in production of dental amalgam, B.P apparatus (sphygmomanometers), and thermometers.

  • Agricultural industries

Used in making fungicides

  • Electricity generation

Due to higher boiling point as compared to water, vapors of mercury are being used instead of steam in electrical generating plants.

  • Cosmetic industry

Making mascaras

  • Mercury is used in mercury-vapor lamps (which emit light with UV radiation), and are used in street lights, UV lights and sun lamps.
  • Mercury is used the production of caustic soda (sodium hydroxide) and chlorine.

Health hazards

Toxicity of mercury is primarily caused by inhalation of the vapors, followed by ingestion of soluble compounds, or dermal absorption of mercury. Once released into the air, mercury gets widely dispersed and remain accumulated in the environment. Ultimately, it finds it way to the bottom of water bodies, and is transformed into methyl mercury, which is the more toxic organic form. Traces of methyl mercury contamination have been reported in fish tissues [6].

Isotopes of Mercury

There are 34 isotopes of mercury (mass number from 175-208). In natural form, mercury is a mixture of seven stable isotopes: 196Hg (0.15 percent), 198Hg (9.97 percent), 199Hg (16.87 percent), 200Hg (23.10 percent), 201Hg (13.18 percent), 202Hg (29.86 percent), and 204Hg (6.87 percent).

 

 

REFERENCES

[1] Mary Elvira Weeks, The discovery of the elements. II. Elements known to the alchemists., J. Chem. Educ., 1932, 9 (1), p11

[2]. Rustagi, N., & Singh, R. (2010). Mercury and health care. Indian Journal of Occupational and Environmental Medicine, 14(2), 45–48. http://doi.org/10.4103/0019-5278.72240

[3]. Glacial Ice Cores Reveal A Record of Natural and Anthropogenic Atmospheric Mercury Deposition for the Last 270 Years. United States Geological Survey (USGS) Science for a changing world.

[4]. Brown TJ, Hetherington LE, Hannis SD, Bide T, Benham AJ, Idoine NE, et al. 1st ed. Keyworth, Nottigham: Natural Environment Research Council; 2009. World Mineral Production 2003-07.British Geological Survey

[5] Hammond CR. 81st ed. Cleveland, Ohio: CRC press; 2000. Elements, in Handbook of Chemistry and Physics. Available from: http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf [last accessed on 2010 Apr 8] [Ref list]

[6] National Research Council. Toxicological effects of methylmercury. U.S: National Academies Press; 2000. Board on Environmental Studies and Toxicology. [Ref list]

 

 

Phosphorus

Phosphorus is a non-metal with diverse biological and industrial significance. It was discovered in 1669 by Hennig Brand and has two allotropic forms and eighteen isotopes.

Discovery and History

The discovery of phosphorus as a novel element was carried out by in Hennig Brand in 1669 by evaporating urine. He obtained a white material that burned brilliantly and emitted a glow in the dark when exposed to oxygen [1]. Antoine Lavoisier identified phosphorus as a separate element in 1777. The name phosphorus also has an interesting origin, as Phosphorus is the name of planet Venus in Ancient Greece language and it means “carrier of light” or “light-bringer”. Commercial scale production of phosphorus was started by Brand and later many scientists, including Robert Boyle, used the same method of phosphorus production developed by Brand. In 1680, Boyle introduced the use of phosphorus to ignite wooden splints with tips of sulfur, and these later were developed into matches [2]. Phosphorus was initially used on a wide scale to make poisons, explosives and nerve agents and due to its toxic and lethal properties, it was commonly named as the “devil’s element”. Gottlieb Gahn and Carl Wilhelm (1796) were the first to discover the presence of phosphorus, in the form of calcium phosphate, in the bones. Until 1840s, one of the major sources of phosphorus has been ashes of bones, and until 1840s. Later in 1850s, the presence of phosphate in rocks on the form of calcium phosphate was discovered and the phosphorus production switched form bones to rocks.

Phosphorus

Periodic Table ClassificationGroup 15
Period 3
State at 20CSolid
ColorColourless, waxy white, yellow, scarlet, red, violet, black
Electron Configuration[Ne] 3s2 3p3
Electron Number15
Proton Number15
Electron Shell2, 8, 5
Density1.82 g.cm-3 at 20°C
Atomic number15
Atomic Mass30.97 g.mol -1
Electronegativity according to Pauling2.19

Occurrence

Phosphorus does not exist in free or elemental state in nature. It forms various compounds and is present in large variety of minerals. The most common source of phosphorus is calcium phosphate that is present in rocks. Phosphorus is an element of great biological value. It is the 6th most abundant element in the living systems. The largest natural reserves of phosphorus are present in Arab region. Other countries or regions that are significant producers of phosphorus include Russia, China, Florida and Morocco [3]. The annual production of elemental phosphorus is around 1000,000 tons.

Physical Characteristics

White phosphorus is yellowish white solid, that has a waxy texture. Phosphorus undergoes spontaneous ignition in air and forms pentoxide (P4O10). There are two allotropic forms of phosphorus, red and black, that differ in physical and chemical properties. Red phosphorus (which is formed by heating of white phosphorus at high temperature) ignites on friction. White phosphorus is a highly toxic substance., while red phosphorus is non-toxic [4].  Phosphorus is water insoluble. Black phosphorus is also termed as violet phosphorus and is the least reactive allotrope of phosphorus. It resembles graphite in appearance and structure.

Chemical Characteristics

White phosphorus is very reactive element. In the presence of oxygen, white phosphorus emits a light green glow, termed as chemiluminescence (glow caused by cold chemical reaction) [5]. The most abundant compounds of phosphorus contain the tetrahedral anion of phosphate (PO43-). There is a vast variety of phosphorus compounds including oxoacids (phosphoric acid), sulfides, nitrides (phosphorus nitride halogens (F2PN, Cl2PN), and phosphides (reaction of metals with red phosphorus). Phosphine (PH3) is a toxic compound with pungent smell, is structural analogue of ammonia. Diphosphine (P2H4), is an analogue of hydrazine and is highly flammable.

Uses and Significance

  • The largest use of phosphorus is in the production of fertilizers. It is an essential nutrient for the growth of plants.
  • Phosphorus is used in making of safety matches, and various ammunitions, such as incendiary shells and hand grenades etc.
  • Phosphorus is used in the manufacturing of bronze and steel.
  • It is used in making LEDs (light-emitting diodes).
  • Phosphorus is used in making detergents, that functions to remove water hardness and improve the efficiency of detergent.
  • It is used in synthesis of nerve agents.
  • It is used as active ingredient in various pesticides.
  • Phosphoric acid is widely used in manufacturing of soft drinks, baking powder.
  • Various compounds of phosphate are used in processing of cheese and meat.

Health Hazards

Phosphorus in the form of phosphate is a vital compound for all living systems. The energy currency of cell, ATP (adenosine triphosphate) that regulates every process in the living cell, uses phosphate. Phosphorylation, that is the process of adding phosphate to various biological molecules, is an important regulatory mechanism in living organisms. Lipids in combination with phosphorus (phospholipids) are the primary building blocks of cell membrane. Phosphorus is present in the building blocks of RNA and DNA. A balanced diet includes a definitive everyday intake of phosphorus. About 0.7 kg of phosphorus is present in an average adult human being, mostly in teeth and bones and in soft tissues of the body. deficiency of phosphate in the body can lead to various physiological effects, including tissue weakness, neurological defects and lack of ATP. Increased intake of phosphate can cause hardening of tissues and organs and diarrhea.

Isotopes of Phosphorus

There are twenty-three isotopes of phosphorus, that range in atomic numbers from 26 to 43. Natural phosphorus constitutes only one stable isotope, phosphorus-31 [6].

 

  

REFERENCES

[1]. Beatty, Richard (2000). Phosphorus. Marshall Cavendish. p. 7. ISBN 0-7614-0946-7.

[2]. Peter Baccini; Paul H. Brunner. Metabolism of the Anthroposphere. MIT Press, 2012. p. 288. ISBN 0262300540.

[3]. Philpott, Tom (March–April 2013). “You Need Phosphorus to Live—and We’re Running Out”. Mother Jones.fwhi

[4]. Abundance. ptable.com

[5]. Michael A. Sommers. Phosphorus. The Rosen Publishing Group, 2007. p. 25. ISBN 1404219609.

Nickel

Nickel is a transition element and is present in U.S five cent coin, which is composed of 75% copper and 25% nickel. It is second most abundant element and is being widely used in making metal alloys and electronics.

History and Discovery

German Miners extract copper from nickel ores in Saxony in 15th century and referred that metal ‘’Kupfernickel’’, which was a term used for useless person, as nickel had a deceptive silver color and was apparently valueless.  Pure nickel was successfully extracted by Baron Axel Fredrik Cronstedt in 1751 [1].  Commercial mining of nickel started in1848 in Norway. And the first pure nickel coin was made in 1881 [3]. In 1889, James Riley proposed that  nickel could be used to strengthen steels products. In 1883, large deposits of nickel were found in Sudbury Basin in Canada, and then later in Russia, Merensky Reef, and South Africa.

Nickel

Periodic Table ClassificationGroup 10
Period 4
State at 20CSolid
ColorSilver with a gold tinge
Electron Configuration[Ar] 3d8 4s2
Electron Number28
Proton Number28
Electron Shell2, 8, 16, 2 or 2, 8, 17, 1
Density8.9 g.cm-3 at 20°C
Atomic number28
Atomic Mass58.69 g.mol -1
Electronegativity according to Pauling1.91

Occurrence

Nickel is present in the earth’s crust and in the inner cores. . It is the is fifth most abundant element of earth crust.  It is main constituent of meteorites and siderites [2]. Nickel most commonly occur in the form of ores, in combination with sulfur andiron in pentlandite (iron nickel sulfide), with arsenic and sulfur in nickel galena. Bulk quantity of nickel is present in two types of ores: laterite, in which mineral mixture is nickeliferous limonite (Fe, Ni) O(OH) and garnierite. Land based resources is about 130 million tons in which 60% is in laterites and 40% is in sulfides form [3]. Ore deposits found in Russia, South Africa, Caledonia, Australia, Cuba, and Indonesia [4]. China is the largest producer of   nickel in the world.

Physical Characteristics

Nickel is a silvery white hard metal. It is soft and ductile in nature. Nickel is ferromagnetic and a fair conductor of heat and electricity. Its symbol is ‘’Ni’’ and its atomic number is 28. Its atomic weight is 58.69. Nickel curie temperature is 355°C, which means above this temperature nickel becomes non-magnetic. Its density is 8.90 g/cm3 at 250C.  Nickel belongs to transition metals in periodic table.

Chemical Characteristics

In combination with iron, nickel is stable.  Elemental nickel strongly reacts with oxygen, especially in powder form due to increased surface area. In large pieces of nickel, the reaction with oxygen is slow due to formation of oxides layer which prevent corrosion. This property provides strengthen and resistant to carrion in metal alloys and is helpful to be shaped into wire, rods, tubes and sheets. Nickel is resistant to actions of alkalis, and slowly react with strong acids and liberate hydrogen and forms Ni2+ ions. It exhibits oxidation states of -1, 0, +2, +3 and +4, and +2 is most common [5]. Ni(I) complexes are very uncommon. They are important for nickel containing enzymes, such as enzymes which catalyze reversible reduction of proton. Ni2+ forms many complexes which have industrial application, for instance nickel chloride, nickel nitrate and nickel sulfamate are used in electroplating baths as well as for preparation of catalyst and textile printing. Nickel ferrites is used for making magnetic core in transformers. Most compounds occur in nature are in combination with arsenic, antimony and sulfur. Nickel with zero oxidation state is carrier of carbon monoxide and is used in the preparation of plastics. Nickel with three oxidation state forms oxide hydroxide and is used as cathode in rechargeable batteries, Ni (IV) is rare oxidation state of nickel form very few compounds.

Significance and Uses

  • Nickel used in making of stainless steel and corrosion resistant alloys.
  • Copper- nickel alloys used in desalination plants for converting sea water into fresh water.
  • Nickel is used in the manufacturing of glass with greenish tint.
  • It is widely used as a catalyst for hydrogenation of vegetable oils to make vegetable ghee.
  • Nickel is used in ceramics industry.
  • Nickle is widely used as decorative silver
  • As foam used in gas diffusion electrodes
  • Nickel used in nickel-cadmium batteries and nickel metal hydride batteries that are used in hybrid cars.
  • Nichrome (nickel chromium) resists corrosion and is used in the making of toaster and electric ovens.
  • Nickel is used in making burglar proof vaults.
  • Nickel can tolerate temperature up to 1000 °C so it is useful in high performance jet engines.
  • It is used as additive in manufacturing of cast iron and steel.
  • It is also used in pendulum rods, weighing machines and measuring devices.
  • Nickel is used in petroleum industry as a catalyst and intermediate in metallurgical industry.

Health affects

Most common health effect of nickel is contact allergic dermatitis. Women are more sensitive than men. Nickel toxicity is primarily an occupational hazard, as worker exposed to nickel become sensitive and develop asthma, chronic bronchitis, reduced lung function, lung cancer and nasal sinus. Nickel allergy is caused due to direct contact of earrings, coins, cellphones and glass frames. Nickel is essential for growth in plants. In the absence of nickel, bean plants produced deformed leaflet tips. Nickel is helpful in breakdown of urea at certain stage in the growth cycle of plants.

Isotopes of Nickel

There are thirty-five isotopes of nickel which range in atomic weight from 48Ni to 78Ni. Nickel has five stable isotopes (nickel-58, nickel-60, nickel-61, nickel-62 and nickel-64) and rest are unstable. 58Ni is most abundant isotopes (68.0775%).

References

  1. https://www.thebalance.com/metal-profile-nickel-2340147
  2. https://periodic.lanl.gov/28.shtml
  3. https://en.wikipedia.org/wiki/Nickel
  4. https://periodic.lanl.gov/28.shtml
  5. https://www.britannica.com/science/nickel-chemical-element

 

Indium

Indium is characterized as post transition metal. It was discovered it 1863 and have found wide use in making semiconductors and transistors. Indium has no biological role but is toxic when inhaled or ingested.

Discovery and History

In 1863, Hieronymous Richter and Ferdinand Reich discovered indium by spectroscopic methods. The name indium was given to the novel element for its indigo blue line in its spectrum. Its symbol is In.  Pure indium was isolated in 1864 [1]. In its early days, indium was used as a coating agent of bearing of aircraft engines in World War II. In 1950, indium beads were used in junction transistors.

Indium

Periodic Table ClassificationGroup 13
Period 5
State at 20CSolid
ColorSilvery lustrous gray
Electron Configuration[Kr] 4d10 5s2 5p1
Electron Number49
Proton Number49
Electron Shell2, 8, 18, 18, 3
Density7.31 g.cm-3 at 20°C
Atomic number49
Atomic Mass114.82 g.mol -1
Electronegativity according to Pauling1.78

Occurrence

Indium is present in Earth’s crust in around 0.21 ppm. It is not present in elemental or free form. Indium does not have any ore that contain high concentration of this metal. Naturally, it is present in little amounts with ores of copper, lead, iron and zinc. Commercially, indium is obtained as a byproduct during the refining of zinc sulfide ores. The largest producer of indium is China, followed by Canada, Japan and South Korea [2].

Physical Characteristics

Indium is a silver white lustrous metal. It is soft and can be cut with a knife. Indium has a low melting point (156.60 C) and boiling point is 2072 C. The density of indium is 7.31 g/cm3. Indium has the ability to become a superconductor below the critical temperature. Indium is resistant to corrosion.

Chemical Characteristics

Indium is not very reactive metal. it does not form compounds with water. Reaction of halogens with indium lead to the production of indium (III) compounds. Indium does not react with base and is insoluble in alkaline solutions. When burned in air, indium (III) forms indium oxide, which can react with both acids and base (an amphoteric compound). The most common oxidation state of indium is +2.

Significance and Uses

  • Indium is widely used in the semiconductor industry. It is used in the manufacturing of LCD screens for television and computer monitors. This accounts for around half of the worldwide usage of indium [4].
  • indium oxides are used as conductive coating on glass in electroluminescent panels.
  • Indium is used in the manufacturing of ultra-high-vacuum applications, such as various electron and X-rays electro-photon spectroscopy.
  • It is used in cryogenic applications for the study and production of various materials at low temperature.
  • Indium is used in amalgam alloys used for dental purposes.
  • It is used as control rod in nuclear reactors.
  • Radioactive isotope of indium (indium-111) is used in nuclear medicine studies for the movement of blood cells in the body.

Health Hazards

Indium (III) is toxic to the body if ingested. It damages the kidneys and is more toxic in aqueous solution as compared to direct injection of metal into the body [5]. Indium toxicity is mostly an occupational hazard and personals can develop symptoms of toxicity through ingestion, eye contact, inhalation and contact with skin.

Isotopes of Indium

Indium has thirty-nine isotopes, which range in mass number from 97 to 135. There are only two naturally occurring isotopes, indium-113 and indium-115. The only stable isotope is indium-113. And indium-115 is the most abundant isotope. Among the artificial isotopes, indium-111 is the most stable with half life of 2.8 days. All indium isomers undergo decay via isomeric transition [6].

 

REFERENCES

 [1]. J.W. Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry., 1929, vol v, Longmans, Green and Co., p 387,388

[2]. Indium – in: USGS Mineral Commodity Summaries (PDF). United States Geological Survey. 2017.

[3]. “Indium Price Supported by LCD Demand and New Uses for the Metal”. Geology.com. Archived from the original (PDF) on 2007-12-21. Retrieved 2007-12-26.

[4] “Indium Price Supported by LCD Demand and New Uses for the Metal”. Geology.com. Archived from the original (PDF) on 2007-12-21. Retrieved 2007-12-26.

[5]. Castronovo, F. P.; Wagner, H. N. (October 1971). “Factors Affecting the Toxicity of the Element Indium”. British Journal of Experimental Pathology. 52 (5): 543–559. PMC 2072430. PMID 5125268.

[6]. Audi, Georges; Bersillon, O.; Blachot, J.; Wapstra, A. H. (2003). “The NUBASE Evaluation of Nuclear and Decay Properties”. Nuclear Physics A. 729 (1): 3–128. Bibcode:2003NuPhA.729….3A. CiteSeerX 10.1.1.692.8504. doi:10.1016/j.nuclphysa.2003.11.001.

 

Oxygen

Oxygen is a highly reactive non-metal and is one of the most significant elements present on the Earth. It is widely used in various manufacturing processes and is the element that sustains the life.

 Discovery and History

The discovery of element as a unique element dates to 2nd century when Philo observed the association of process of combustion with presence of air. Robert Hook, in 1665 proposed the presence of unique substance in air that is released when potassium nitrate is heated. Later, John Mayow (1668) proposed that there is a certain element termed as “nitoarial spirit” (for oxygen) present in air that is consumed in combustion and respiration. In 1774, Carl Wilhelm Scheele and Joseph Priestley independently discovered oxygen, and named it “fire air” and “dephlogisticated air”, respectively due to its role in combustion. The name oxygen originates from combination of two words, oxys and genes, that are Greek word for “acid forming”. The name was first proposed by Antoine Lavoisier [1].

Oxygen

Periodic Table ClassificationGroup 16
Period 2
State at 20CGas
ColorColorless gas
Electron Configuration[He] 2s2 2p4
Electron Number8
Proton Number8
Electron Shell2, 6
Density1.43 g.cm-3 at 20°C
Atomic number8
Atomic Mass15.99 g.mol -1
Electronegativity according to Pauling3.44

Occurrence

Oxygen is considered as the most abundant element in the biosphere of Earth, by mass. Biosphere involves the land, sea and air that support life. Oxygen constitutes around 49.2% of Earth’s crust [2]. Oxygen is the third most abundant element in the Universe. The most common allotrope of elemental oxygen is dioxygen O2. It is primarily present in the atmosphere of the Earth and is a major part of gaseous content of the biosphere. Oxygen is the 2nd most abundant component of Earth’s atmosphere (present in about million billion tons or 21% of earth’s atmosphere). Another allotrope of oxygen, known as ozone, is a trioxygen molecule. Ozone is present in the upper atmosphere and provides protection against harmful UV rays form sun by absorbing them. Oxygen is a major component of the water bodies on Earth and constitutes around 88.8% by mass of oceans [3]. The production of free oxygen on Earth started around 3.5 billion years ago and lead to a gradual increase over the centuries. The aerobic environment and the significantly high concentration of oxygen on earth is attributed to the oxygen cycle. Oxygen is continuously replenished into the Earth’s environment, by the outstanding process of photosynthesis (a process by which light energy from sun splits water molecule to release free oxygen). Elemental or free oxygen is present in solution form in water bodies, where it plays crucial role in providing support to ocean life. About 45-70% of environmental oxygen content is provided by green algae and cyanobacteria, while rest is contributed by the terrestrial plants [4]. Cellular respiration is a vital energy production phenomenon that occurs in all plants and animals, and lead to oxygen consumption while photosynthesis continuously replenish the oxygen being consumed.

Physical Properties

Oxygen is a colorless, tasteless and odorless gas. It readily dissolves in water, and more conveniently in freshwater as compared to seawater. The freezing point of oxygen is −218.79 °C, and it condenses at −182.95 °C. Oxygen, in both of its liquid and solid state, appear as clear, sky-blue color compound. Oxygen is highly combustible element but not flammable. It only helps in burning but does not burn itself.  Oxygen is a poor conductor of electricity and heat. Oxygen is denser than air (1.429 grams per liter) [5].

Chemical Properties

Oxygen is a very reactive element. Oxygen has an oxidation state of -2 in almost all compounds. While -1 is present in some peroxides [6]. The most common compound of oxygen is water, which is an oxide of hydrogen. Oxygen has a high electronegativity. Oxygen is also present in the form of carbon dioxide in trace amount in the atmosphere. Oxygen compounds including various silicates (silicon-oxygen mineral) are abundantly present in the mantle and crust of the Earth. Oxygen also reacts with transition metals and form dioxygen complexes with them, such as myoglobin and hemoglobin (oxygen carrying proteins present in the blood). Various significant organic compounds also contain oxygen, including citric acid glycerol, acetic anhydride and acetamide. The most common reaction of oxygen is termed as oxidation. Ozone is a powerful oxidizing agent [7]

Significance and Uses

  • The most common use of oxygen is in melting, refining and manufacturing of steel and various metals.
  • It is widely used in the manufacturing of various chemicals.
  • Oxygen is widely used in making life support kits and storage for medical and recreational activities.
  • Oxygen is used in making oxyacetylene for welding.
  • It is used as oxidant in rocket propellent, by combining hydrogen with liquid oxygen.
  • It is used in purification processes of various metals.

Health Hazards

At high levels oxygen acts as a toxic gas. Prolonged exposure to high levels of oxygen present at a partial pressure of more than 50 kilopascals, can lead to various health effects, including convulsion, difficulty in breathing and unconsciousness. The use of oxygen incubators for premature babies have been ceased due to toxic effect of high oxygen levels that led to blindness. Oxygen helps combustion, so concentrated sources of oxygen can be a potential risk of explosion or fire.

Isotopes of Oxygen

There are three isotopes in naturally occurring oxygen: oxygen-16, oxygen, -17 and oxygen-18. These are stable isotopes of oxygen and oxygen-16 is the most abundant of all isotopes with a natural abundance of 99.76%. There are fourteen radioactive isotopes of oxygen [8].

 

 

REFERENCES

 [1]. Mary Elvira Weeks, The discovery of the elements. IV. Three important gases., J. Chem. Educ., 1932, 9 (2), p 215

[2]. “Oxygen”. Los Alamos National Laboratory. Archived from the original on October 26, 2007. Retrieved December 16, 2007.

[3]. Cook & Lauer 1968, p. 500

[4]. Fenical, William (September 1983). “Marine Plants: A Unique and Unexplored Resource”. Plants: the potentials for extracting protein, medicines, and other useful chemicals (workshop proceedings). DIANE Publishing. p. 147. ISBN 978-1-4289-2397-3.

[5]. “Oxygen Facts”. Science Kids. February 6, 2015. Retrieved November 14, 2015.

[6]. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9., p. 28

[7]. http://www.elementalmatter.info/oxygen-properties.htm

[8]. Oxygen Nuclides / Isotopes”. EnvironmentalChemistry.com. Retrieved December 17, 2007.

 

Chromium

Chromium is a transition metal that was discovered by Gottlob Lehmann in 1766. It has a shiny surface that is resistant to corrosion and this quality makes its ideal for manufacturing and coating of wide range of material, including cars and bikes.

History and Discovery

Chromium was initially discovered in red crystalline mineral form, known Siberian red lead, by Johann Gottlob Lehmann (1766). Later, chromium was discovered as a novel, and isolated metal by Louis-Nicolas Vauquelin in 1797. The name chromium has been derived from Greek word, chroma, which means color. The name was given to this metal as it exists in diverse colors and was suggested by, Antoine Francois de Fourcroy (1755-1809) and René-Just Haüy (1743-1822). Chromium has a distinct shine and forms various compounds in different colors that include green, purple, black, yellow, and orange [1].

 

Chromium

Periodic Table ClassificationGroup 6
Period 4
State at 20CSolid
ColorSilvery metallic
Electron Configuration[Ar] 3d5 4s1
Electron Number24
Proton Number24
Electron Shell2, 8, 13, 1
Density7.19 g.cm-3 at 20°C
Atomic number24
Atomic Mass51.99 g.mol -1
Electronegativity according to Pauling1.66

Occurrence

Chromium is the 13th most abundant element in the Earth’s crust [2]. Chromium is not present in free form. It is present in form of various ores, and the most common ore is iron chromium oxide FeCr 2 O4, which is termed as chromite. Chromite is the principal source of chromium that is used in pigments, worldwide. Chromium is released in the environment by erosion of rocks that contain chromium. Volcanic activities also play important role in the distribution of chromium. The largest producer of chromite is South Africa, followed by India, Brazil, Turkey, Finland and Kazakhstan [3]. Russia has deposits of the rare native form of chromium in Udachnaya Pipe, from which native chromium and diamonds are extracted. The annual production of chromite is about 28.8 million metric tons, which is primarily being used in the production of steel.

Physical Characteristics

Chromium is steel-gray in color. It is shiny, hard and brittle metal, that is easy to break. The density of chromium is 7.1 g.cm-3. Chromium has a highly polishable texture. It is resistant to tarnishing upon exposure with air. Chromium has outstanding magnetic properties. It is very dense metal and has a thermal conductivity of 93.9 W [4].

Chemical Characteristics

Chromium form variety of compounds and exists in many oxidation states, including +3, +6, +1. +4 and +5. The predominant and most stable oxidation state of chromium is +3 [5]. Large number of chromium [III] compounds are present, such as compound of chromium with sulfuric and hydrochloric acid. Chromium (VI) compounds, including chromate anion (CrO42-), are powerful oxidizing agents.

Significance and Use

  • The widest usage of chromium is in the making of metal alloys. Chromium can impart strength corrosion resistance and shine to various metals and is widely used in the manufacturing of steel.
  • Chromium is widely used as coating agent, as it is highly durable and strong as compared to other metals. Chromium plating is used for bikes and cars.
  • Chromium has been widely used in the manufacturing of dyes, pigments and paints due to its unique and wide range of colors.
  • Chromium oxides are used for dying glass and ceramics. It imparts natural green color and is also used by armed forces to paint their tanks and vehicles to imitate infrared reflectance of green leaves and give them camouflage.
  • Chromium is widely used for tanning of leather. Chromium has the ability to cross link the collagen fibers of leather and provide stability.
  • Chromium is used in the making of blast furnace, kilns, brick mold and sand in foundry for casting of metals.
  • Chromium compounds (with acids) are used for cleaning purposes due to their oxidizing properties.

Health Hazards

Chromium has a significant role in the body of living organisms. In humans, chromium plays crucial role in the metabolism of sugar in the body. Chromium deficiency is also linked with diabetes by affecting the function of insulin (a hormone that plays important role in the metabolism of sugar, proteins and fat) [6]. In contrast, Cr (VI) is highly toxic compound. It can lead to mutagenic effect and lung damaging effects if inhaled. If Cr (VI) is ingested in contaminated water, it can lead to various stomach complications, including tumors. The range of oral toxicity concentration is 50 to 150 mg/kg of Cr (VI). Skin contact with hexavalent chromium can aggravate allergic reaction termed as allergic contact dermatitis [7]. Chromium can enter our body through food cooked in stainless steel pots. Chromium (III) is also considered toxic and have mutagenic effects on DNA [8]. Large amounts of chromium compounds are being released into environment by various industries, tanneries (paints, dyes, leather manufacturing), and pose threat of contamination of soil and water.

 Isotopes of Chromium

Natural chromium has four isotopes: chromium-50, chromium-52, chromium-53, chromium-54. There are twenty-one other isotopes of chromium. Chromium-53 is the most abundant among all isotopes. Several isotopes of chromium are used for medical purposes. For instance, chromium-51 is used for studying survival and growth of red blood cells and for measuring blood volume [9].

 

 

 REFERENCES

[1]. Per Enghag, Encyclopedia of the elements: technical data, history, processing, applications.,p 577- 578, John Wiley and Sons, 2004

[2]. Emsley, John (2001). “Chromium”. Nature’s Building Blocks: An A-Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 495–498. ISBN 978-0-19-850340-8.

[3]. Papp, John F. “Mineral Yearbook 2015: Chromium” (PDF). United States Geological Survey. Retrieved 2015-06-03.

[4]. http://www.chemistryexplained.com/elements/A-C/Chromium.html

[5]. Clark, Jim. “Oxidation states (oxidation numbers)”. Chemguide. Retrieved 3 October 2018

[6] Chromium”. Office of Dietary Supplements, US National Institutes of Health. 2016. Retrieved 26 June 2016.

[7]. “ToxFAQs: Chromium”. Agency for Toxic Substances & Disease Registry, Centers for Disease Control and Prevention. February 2001. Archived from the original on 2014-07-08. Retrieved 2007-10-02.

[8]. Eastmond, David A.; MacGregor, J. T.; Slesinski, R. S. (2008). “Trivalent Chromium: Assessing the Genotoxic Risk of an Essential Trace Element and Widely Used Human and Animal Nutritional Supplement”. Critical Reviews in Toxicology. 38 (3): 173–190. doi:10.1080/10408440701845401. PMID 18324515.

[9]. Naturally occurring isotope abundances: Commission on Atomic Weights and Isotopic Abundances report for the International Union of Pure and Applied Chemistry in Isotopic Compositions of the Elements 1989, Pure and Applied Chemistry, 1998, 70, 217. [Copyright 1998 IUPAC]

Gold

Gold is a precious metal which has been in human use since 2000 BC. It is unreactive and is highly resistant to corrosion which makes it favorable for wide range of medicinal, ornamental and structural use.

History and Discovery

Gold is the metal of prehistoric times and it was collected from water streams in form of particles. The Egyptians in around 2000 BC started mining of gold. And gold made items, such as masks, graves etc. have been found to contain gold from civilization of 3800 to 2000 BC. Pure gold has been found from around 6000 years ago Israel kingdom [1]. Gold coins were made in the reign of King Croesus of Lydia (modern Turkey) (561-547 BC).  Gold has been considered as perfect and precious metal since ancient times, and long relentless but in vain efforts have been made over centuries to transform various metals into gold, a concept known as alchemy. The word gold has been originated from the word “geolo” used by Anglo-Saxon civilization that inhabited England in the 5th century. Geolo (Sanskrit origin meaning to shine) means yellow. The symbol of gold comes from a word of Latin origin, aurum, which is originated from Aurora, which is the goddess of morning glow [2].

Gold

Periodic Table ClassificationGroup 11
Period 6
State at 20CSolid
ColorMetallic yellow
Electron Configuration[Xe] 4f14 5d10 6s1
Electron Number79
Proton Number79
Electron Shell2, 8, 18, 32, 18, 1
Density19.32 g.cm-3 at 20°C
Atomic number79
Atomic Mass196.97 g.mol -1
Electronegativity according to Pauling2.54

Occurrence

Gold is widely present in the Earth’s crust (0.3 ppm by weight). It is also present in river beds as rock bound gold is released by erosion of rock by running water. Gold also exists in the form of alloy, such as amalgam (with mercury) or with silver. Gold is found in association of pyrites deposits and from quarts and gravels.  Naturally, most of the gold present in the Earth’s crust is in combination with silver. The term “electrum” is used for gold ore that have silver content of more than 20%. The biggest producer of gold is China from around two third of the gold (around 455 tons) in world is produced. The other countries where gold is being mined include USA, Canada and Russia. The annual production of gold in the world is 2500 tons per year. Oceans, including the Northeast Pacific and Atlantic contain about 10–30 parts per quadrillion, that makes about 10–30 g/km3 of gold in form of flakes or nuggets [3].

Physical Characteristics

Gold is a reddish yellow metal. It is highly ductile and malleable. Gold is a soft metal and is usually used in alloyed form to provide strength and durability. About 1 ounce of gold can be hammered or pressed into 300 square feet sheet. The unit carat is used for the percent purity of gold, especially in jewellery. Twenty-four carats gold is considered as pure gold. Gold has the ability to conduct heat and electricity with great efficiency. And is considered as a fairly dense metal with density of 19.32 g/cm3 [4].

Chemical Characteristics

Gold is an inert metal and considered as the most noble metal. However, these are many diverse forms of gold, with oxidation number ranging from -1 to +5. The dominant form of gold is Au(I) and Au (III). Gold is resistant to attack by oxygen at any temperature. Gold is unreactive and resistant to most acids. It can dissolve in a mixture of hydrochloric acid and nitric acid, known as aqua regia. Gold is also soluble in alkaline solutions of cyanide. Gold forms amalgam with mercury but it does not involve a chemical reaction. Gold is highly resistant to corrosion. Gold can react with certain halogens, such as fluorine to form gold (III) fluoride. Gold in powdered form can react with chlorine to form gold chloride. Various alloys of gold are formed to alter the strength and hardness of gold and create exotic colors [5].

Uses and Significance

  • Gold is a precious metal and widely used in making of jewellery, coinage, crowns and decorative items.
  • It is widely used in making components of computerized devices, such as corrosion resistant electrical conductors.
  • Gold is used in the glass industry for making colored-glass.
  • It is used as fillers in tooth restoration.
  • Certain salts of gold are used for medicinal purpose.
  • Flakes of gold are used in various drinks and sweets.
  • Gold plating is used in helmets used by astronauts as gold due to its inert nature can provide protection against dangerous and harmful effects of solar radiations.
  • Radioactive isotope of gold (Au-198) has been used to treat various cancers including prostate and bladder.

Health Hazard

Gold is a non-toxic metal. It may cause irritation in eye or skin and prolonged exposure can lead to irritation in lungs. There is no ecotoxicity of gold as it is insoluble in water. Gold is used for therapeutic purpose in a treatment called Chrysoteraphy, for relieving pain in rheumatoid arthritis. Recently, gold particles based anti-cancer drugs have been investigated.

Isotopes of Gold

There are 35 isotopes of gold, with mass numbers ranging from 171 to 205. These are the artificially produced isotopes of gold. The natural gold consists of one stable isotope, Au-197, which is the only stable isotope. The isotopes with atomic masses above 197 decay by emission of β rays [6].

 

REFERENCES

[1]. Gopher, A.; Tsuk, T.; Shalev, S. & Gophna, R. (August–October 1990). “Earliest Gold Artifacts in the Levant”. Current Anthropology. 31 (4): 436–443. doi:10.1086/203868. JSTOR 2743275.

[2]. Eric. J. Holmyard, Makers of Chemistry., 1931, Oxford at the Clarendon Press. p163

[3]. Kenison Falkner, K.; Edmond, J. (1990). “Gold in seawater”. Earth and Planetary Science Letters. 98 (2): 208–221. Bibcode:1990E&PSL..98..208K. doi:10.1016/0012-821X(90)90060-B.

[4]. https://www.webelements.com/gold/physics.html

[5]. https://sciencestruck.com/chemical-properties-of-gold

[6]. “Nudat 2”. National Nuclear Data Center. Retrieved 12 April 2012

 

Hydrogen

 Hydrogen is one of the three most abundant elements present on Earth. It was discovered in 1766 by Henry Cavendish and is widely used for various industrial, medical and recreational purposes.

Discovery and History

The informal discovery of hydrogen dates to 1500s when Paracelsus (alchemist) observed the production of bubbles (gas) when sulfuric acid was added to iron and later Robert Boyle (1671) observed the production of same flammable bubbles. But the formal discovery of hydrogen was reported by Henry Cavendish (1766), who analyzed the bubbles and showed that burning of hydrogen lead to the production of water. Hence the gas was named hydro-genes (1783 by Antoine Lavoisier), which is the Greek word for “water-former”. In 1898, James Dewar successfully liquified hydrogen [1]. In as early as 1783, hydrogen gas was used in air balloons by Jacques Charles, which demonstrated the power and reliability of hydrogen for providing the lift for air-travel. And later, Henri Giffard (1852), made the first hydrogen-lifted airship. Hydrogen-lifted airships found tremendous usage in the World War 1, where they were used for transferring people, as observation platforms and as bombers. Hydrogen also has a notorious event related to its name, the incident of Hindenburg airship (1937), were combustion of hydrogen led to the destruction of the ship in the midair and brought an end to the era of hydrogen-based air-travels [2].

Hydrogen

Periodic Table ClassificationGroup 1
Period 1
State at 20CGas
ColorColorless gas
Electron Configuration1s1
Electron Number1
Proton Number1
Electron Shell1
Density0.09 g.cm-3 at 20°C
Atomic number1
Atomic Mass1.01 g.mol -1
Electronegativity according to Pauling2.20

Occurrence

Hydrogen is ubiquitous in nature as it is present in water. It is considered as the 3rd most abundant element in the Earth’s atmosphere and the most abundant element in the universe. Hydrogen is the main component of living systems (hydrocarbons). [3]. Hydrogen is found in significant abundance in undetected form of mass, such as dark matter, and in gas giant planets and stars. In gaseous form, it is present only in a small fraction and makes around 1 part per million in volume.  Hydrogen is mostly present in its atomic and plasma states, which have significantly different properties as compared to the molecular (gaseous) form. In its plasma form, hydrogen give rise to natural phenomenon of Birkeland currents and aurora (by interacting with magnetosphere of the Earth). The neutral atomic state of hydrogen is mainly present in the interstellar medium ISM (outer space) [4].

 Physical Characteristics

Hydrogen gas is the lightest of all gases. It has the lowest density (0.0899*10 -3 g.cm -3 at 20 °C) as compared to all other gases. Hydrogen is odorless and colorless gas. It is non-toxic and nonmetallic at standard conditions (standard temperature and pressure). Hydrogen has an atomic number of 1 and atomic mass of 1.007825g.mol-1. It has a boiling point of -252.8C and a melting point of -259.2 C.

 Chemical Characteristics

Hydrogen is a highly (combustible) flammable gas. Hydrogen is more soluble in organic solvents and less soluble in water. At room temperature, hydrogen is stable and unreactive. However, under different environmental conditions, various metals absorb hydrogen, such as the absorption of hydrogen by steel can cause brittleness in steel [5]. Hydrogen becomes highly reactive at higher temperatures. And lead to the dissociation of its diatomic form into free atom of hydrogen, which is highly reactive and a powerful reducing agent. Free hydrogen radical can react with chlorides and oxides of various metals to form free metals. It can lead to the formation of hydrides of various metals, non-metals such as, H2S, NAH, PH3 and KH. One of the most common compounds produced by elemental hydrogen is hydrogen peroxide (H2O2) with oxygen. The light atomic nature of hydrogen impart various favorable properties to it, including low viscosity, and high thermal conductivity and specific heat as compared to all other gases.

Significance and Uses

  • Hydrogen is widely used to produce ammonia.
  • The reaction of combination of hydrogen atoms is quite exothermic. And this heat is used in atomic hydrogen welding process.
  • Hydrogen is widely used for the catalytic hydrogenation process, which is used in the production of vegetable ghee from vegetable oil (unsaturated fats to saturated fats).
  • Hydrogen is becoming popular as green fuel (clean fuel, with no emission of carbon dioxide or other toxic compounds). Various fuel cells are being manufactured for making internal combustion engines for making pollution free buses and cars.
  • Hydrogen is used as rocket fuel and as rocket propellent.
  • Hydrogen provides protective and stable atmosphere for the production of flat glass sheets in glass industry.
  • It is used in electronic industry for the manufacturing of silicon chips (as flushing gas).
  • Hydrogen is widely used in power stations as a coolant in generators.

Health Effects of Hydrogen Gas

Hydrogen is toxic to the body and can absorbed by inhalation which can lead to oxygen deficiency in the body. affected individuals lead to hypoxia and show symptoms such as headaches, dizziness, ringing in ears, nausea, vomiting and unconsciousness. If untreated, victim can turn blue and it can be fatal. When hydrogen is exposed to air, it can lead to formation of explosive mixtures. Heating of hydrogen can also cause violent combustion or explosion [7].

Isotopes of Hydrogen

There are three naturally occurring isotopes of hydrogen, named 1H (protium), 2H (deuterium), and 3H (tritium). Protium is the most abundant hydrogen isotope (99.98%). Tritium is the most stable radioisotope and have a half-life of 12.32 years. All heavier isotopes of hydrogen are synthetic and are extremely unstable. Deuterium has found major applications in nuclear magnetic resonance studies [6].

 

  

REFERENCES

[1]. Presenter: Professor Jim Al-Khalili (21 January 2010). “Discovering the Elements”. Chemistry: A Volatile History. 25:40 minutes in. BBC. BBC Four.

[2]. Emsley, John (2001). Nature’s Building Blocks. Oxford: Oxford University Press. pp. 183–191. ISBN 978-0-19-850341-5.

[3]. Miessler, G. L.; Tarr, D. A. (2003). Inorganic Chemistry (3rd ed.). Prentice Hall. ISBN 978-0-13-035471-6

[4]. Gagnon, S. “Hydrogen”. Jefferson Lab. Retrieved 5 February 2008.

[5] Rogers, H. C. (1999). “Hydrogen Embrittlement of Metals”. Science. 159 (3819): 1057–1064. Bibcode:1968Sci…159.1057R. doi:10.1126/science.159.3819.1057. PMID 17775040.

[6]. https://www.lenntech.com/periodic/elements/h.htm

[7] https://courses.lumenlearning.com/introchem/chapter/isotopes-of-hydrogen/

ZIRCONIUM

Zirconium is a transition metal discovered in 1789. It is a lustrous metal and is widely used in manufacturing of wide range of durable, strong and noncorrosive materials.

History and Discovery

Several zirconium related minerals, including Zircon have been mentioned in biblical writings. Zirconium was discovered by Martin Klaproth in 1789, and in 1824 Jacob Berzelius (Swedish chemist) isolated an impure form of this metal. Zirconium was isolated in pure form by Anton E. van Arkel and J.H. de Boer (1925). The name Zirconium has been originated from the Persian word zargun, that means “golden colored” [1].  Zirconium came into lime light after the 1940s, when its use in the nuclear power plants was identified.

Zirconium

Periodic Table ClassificationGroup 4
Period 5
State at 20CSolid
ColorWhitish-silver
Electron Configuration[Kr] 4d2 5s2
Electron Number40
Proton Number40
Electron Shell2,8,18,10,2
Density6.49 g.cm-3 at 20°C
Atomic number40
Atomic Mass91.22 g.mol -1
Electronegativity according to Pauling1.2

Occurrence

Zirconium is an abundant metal. The commercial source of zirconium are the alluvial deposits present in beaches of ocean, beds of old lakes and streams. The most abundant mineral form of zirconium is baddeleyite (zirconium dioxide). The most common impurity in zirconium metal is hafnium, but for commercial use (except in nuclear reactors), zirconium with 1% hafnium is considered as pure metal. Today, the biggest producers of zirconium include South Africa, Australia, Indonesia, India, China and Sri Lanka. And around 900,000 tons per year of zircon (ZiSO4) are produced in the world [2].

Physical Characteristics

Zirconium is a grey-white element. It is shiny, lustrous, and malleable transition metal. In powder form, zirconium exists in black color. The physical characteristics of pure and impure form of zirconium greatly vary, as impure zirconium is hard and brittle, while in pure form, it is soft and ductile [3]. Zirconium is lighter than steel (have density of 6.49 g.cm-3 at 20C). The atomic number of zirconium is 40 and its atomic mass is 91.22 g.mol-1. The melting point of zirconium is 1852°C and boiling point is 4400°C. Its oxidation state is +4. It is present in the Group 4 (IV)b of the periodic table [4].

Chemical Characteristics

Zirconium is a resistant metal, with outstanding ability to withstand corrosion and heat. It can absorb significant amounts of various gases, including nitrogen, hydrogen and oxygen. Zirconium reacts vigorously with air and in divided or powder form, it can lead to spontaneous and dangerous ignition. It is unreactive with alkalis and acids and does not dissolve in them. Zirconium does not form radioactive isotopes when bombarded with neutrons [5].

Significance and Uses

  • The most common use of zirconium is in nuclear applications. It is used in the manufacturing of engineering material for nuclear reactors. For instance, zirconium based cladding fuel rods are being used and core structure of reactors is also made from zirconium. Further, zirconium does not readily absorb neutron and can withstand any mechanical damage caused from neutron bombardment in nuclear reactors.
  • Zirconium readily absorbs oxygen which makes it desirable candidate for removing residual gases from electron tubes or vacuum tubes (used in making television or computer screens).
  • Zirconium is used in making refractory materials, including crucibles, rocket launch structures, furnaces, incinerators and ovens.
  • It is used in various ceramic industries for opacification purposes (adjustment of glaze content).
  • Zirconium is used as hardening agent in making alloys, including magnesium and steel.
  • It is widely used in fabrication of valves, and pumps due to its high resistant to corrosion.
  • It is widely used in packaging and paper industry for making surface coats as zirconium have outstanding strength and resistance.

Health Hazards

Zirconium metal and its salts have low toxicity (environmental and biological) as they are scarcely soluble in water. If ingested, zirconium does not get absorbed in the tissues and passes the gut without causing any hazard. Plants also don’t absorb zirconium present in the soil. However, the radioactive isotopes zirconium 95 is a radionuclide with considerably high half-life and continue to persist in the environment and cause cancer risks for decades [5].

Isotopes of Zirconium

Zirconium have five natural isotopes, zirconium-90 (51.46 percent), zirconium-92 (17.11 percent), zirconium-91 (11.23 percent), zirconium-96 (2.80 percent) and zirconium-94 (17.40 percent). There are 28 artificial isotopes of zirconium, which range in atomic mass from 78 to 110. The zirconium-93 is the most stable artificial isotope of zirconium, while zirconium-110 is the least stable isotope (with half-life of around 30 milliseconds). 110Zr is the most radioactive isotope and the heaviest [6].

 

REFERENCES

[1]. Harper, Douglas. “zircon”. Online Etymology Dictionary.

[2]. Nielsen, Ralph (2005) “Zirconium and Zirconium Compounds” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. doi:10.1002/14356007.a28_543

[3]. Emsley, John (2001). Nature’s Building Blocks. Oxford: Oxford University Press. pp. 506–510. ISBN 0-19-850341-5.

[4]. Lide, David R., ed. (2007–2008). “Zirconium”. CRC Handbook of Chemistry and Physics. 4. New York: CRC Press. p. 42. ISBN 978-0-8493-0488-0.

[5] https://www.lenntech.com/periodic/elements/zr.htm

[6]. https://www.britannica.com/science/zirconium