Lead

Lead has been known since old ages and its use has been largely limited due to its high toxicity. It is the heaviest stable element and is resistant to corrosion.

History and Discovery

Lead is a prehistoric metal and was used by people of ancient Rome and Western Asia around 7000 BCE. It was widely used to make water pipes by the Romans and named it as plumbum nigrum (black lead). The use of lead decreased with the fall of the Roman Umpire. Lead was used as a currency in Ancient Chinese courts. Civilizations of Indus valley and Ancient Greece used lead to make amulets, glasses, ornaments, glazes and sinkers in fishing net. The name plumbum, was given to the metal and the English word plumbing was originated from this Latin word. The origin of name of lead is intertwined with tin, as olovo translates to lead in Czech, while it translate to tin in Russian language. The word lead has been derived from Old English word lead.

Lead

Periodic Table ClassificationGroup 14
Period 6
State at 20CSolid
ColorMetallic gray
Electron Configuration[Xe] 4f14 5d10 6s2 6p2
Electron Number82
Proton Number82
Electron Shell2, 8, 18, 32, 18, 4
Density11.35 g.cm-3 at 20°C
Atomic number82
Atomic Mass207.20 g.mol -1
Electronegativity according to Pauling1.87 (+2)

Occurrence

Lead is an abundant metal and is present around 14 ppm in the Earth’s crust. It is considered as the 38th most abundant element on Earth [1]. It is primarily present in combined form with sulfur and is rarely found in elemental or metallic form. The most common mineral of lead is galena (PbS). It is found in zinc ores. There are various impurities in lead minerals and ores, including tin, arsenic, gold, silver and copper. The largest deposits of lead are found in Australia, Russia, China, US, and Ireland [2].

Physical Characteristics

Lead is a silver colored metal with a tint of blue. It tarnishes to dark gray color when exposed to air. Lead is soft but is significantly denser than other metals. it is malleable and has a low melting point. Lead has the atomic number of 82, which is considered as the highest among all stable naturally occurring elements.

Chemical Characteristics

Lead is not very reactive. It belongs to the post-transition metal group in the periodic table. Lead frequently form stable covalent bonds as compared ionic bonding. Lead reacts with acids and bases. The common oxidation state of lead in compounds is +2. Lead can also form bonds with other lead molecule and can acquire unique arrangement, such as rings, chain and polyhedral structures.

Significance and Uses

  • Lead toxicity has led to major decline in its uses since mid-1980s. It is still used in various industries where its toxic effects are minimal for the environment and humans.
  • Lead has been widely used for bullets.
  • It is used in weight belts used by scuba divers to counteract their buoyancy.
  • Lead is used to cover underwater cables as it is resistant to corrosion.
  • It is widely used in construction industry. And is part of gutters, roofing material, cladding etc., to reinforce the structure.
  • Lead is used to make sculptures and statues.
  • Lead alloys with copper, including bronze and brass are used to make components of machinery.
  • Lead is used in lead batteries and various supercapacitors are being used to in US, Australia and Japan in various megawatt scale applications.
  • Lead is used to detect aldehydes, and organic acids (Oddy test).

Health Hazards

Lead is highly toxic element. Its toxicity was recognized in the late 19th century. It can accumulate in bones and soft tissues and damages the neurons and nervous system. Lead has the ability to cross the blood-brain barrier and cause damage to brain and other organs. Lead toxicity is specially alarming for children as it can lead to lifelong neurological disorders, and behavioral challenges. Lead exposure during pregnancy can cause miscarriage and can lead to delay in puberty in girls. Lead is known to interfere with many biologically significant enzymes, including enzyme of heme synthesis pathway [3]. Lead toxicity is primarily caused by the ingestion of lead-based paints, in toys, or in home. Lead dust from furniture or window sill painted with lead can enter the body via hand to mouth contact. Inhalation of lead is the second most common pathway of lead toxicity, and lead from automobiles and cigarette smoking can cause severe toxic effects on the human body. About 100 mg/m3 of airborne lead concentration is considered dangerous to health and life [4]. Lead can persist in our environment, especially organic soil and can remain there for hundreds of years. From contaminate soil and water, lead can enter the food chain and effect animals. It also enters the human body through consumption of contaminated fruits, and vegetables. Lead can accumulate in bodies of marine animals, especially fishes and cause bioaccumulation.

Isotopes of Lead

Lead consist of four stable isotopes, lead-204, lead-206, lead-207 and lead-208 [5]. There are five unstable isotopes of lead. The atomic number of lead is 83, which makes lead the heaviest stable element and isotope-208 is the heaviest stable nucleus. The theoretical half-life of isotopes of lead is around 1035 to 10189. There are around 43 artificial isotopes of lead, and their atomic mass range from 178-220.

REFERENCES

[1]. Elemental abundance figures are estimates and their details may vary from source to source

[2]. United States Geological Survey 2017, p. 97.

[3]. Cohen, Trotzky & Pincus 1981, pp. 904–06.

[4]. National Institute for Occupational Safety and Health.

[5]. IAEA – Nuclear Data Section 2017

Iridium

Iridium belongs to the platinum group of metals and is highly dense and resistant to corrosion. It was discovered in 1803.

History and Discovery

Ancient South Americans and Ethiopians have used platinum along with iridium. Iridium was discovered as an impurity in platinum metal by Smithson Tennant in 1803. When platinum was dissolved in aqua regia, iridium appeared as dark insoluble residue, which was later identified as a new metal. The name iridium was given by Tennant after the Greek goddess Iris (Goddess of rainbow), as the newly discovered metal formed varying color compounds and salts [1].

Iridium

Periodic Table ClassificationGroup 9
Period 6
State at 20CSolid
ColorSilvery white
Electron Configuration[Xe] 4f14 5d7 6s2
Electron Number77
Proton Number77
Electron Shell2, 8, 18, 32, 15, 2
Density22.4 g.cm-3 at 20°C
Atomic number77
Atomic Mass192.22 g.mol -1
Electronegativity according to Pauling2.20

Occurrence

Iridium is an extremely rare element. And is present in about 0.001 ppm in crustal rocks. Iridium is an element of space and is more abundant on meteorites than in Earth’s crust and has an average abundance of 0.5 ppm [2]. Traces of iridium from core samples of Pacific Ocean and Cretaceous-Paleogene boundary support the hypothesis that massive meteorites showers led to extinction of dinosaurs around 66 million years ago. Due to its low reactivity, iridium is found in its elemental form or in the form of natural alloys, including iridium-osmium alloys (idrosmine and osmiridium). Some minerals of iridium have also been found, but they are quite rare, such as cuproiridsite and irarsite. The annual production and consumption of iridium is only three tons.

Physical Characteristics

Iridium is a whitish silver transition metal. It is brittle solid at standard temperature and pressure. It is a significantly dense metal and is considered as the 2nd densest element (22.56 g/cm3). Iridium is considered as the most corrosion-resistant metal and does not react with water or oxygen even at high temperatures [3]. In powdered form, iridium is highly flammable. Indium has very high boiling and melting points. It can become a super conductor at temperature lower than 0.14K [?]. Indium has an extraordinary ability to withstand deformation and is very stiff. Indium is resistant to most acids and alkalis. It is a very costly metal.

Chemical Characteristics

Iridium is considered as a Nobel metal due to its low reactivity. It does not react with molten metals, acids or silicate. However, certain salts, including potassium and sodium cyanide can react with iridium at high temperature. Iridium also reacts with fluorine at high temperature [4].

Significance and Uses

  • Iridium is widely used in electronic industry and is primarily used as a coating agent.
  • Iridium is used as a catalyst in various chemical industries, such as Cativa process that involves the formation of acetic acid from methanol by carbonylation.
  • Alloys of osmium-iridium are used to make compass bearings, tips of fountain pen and balances used for precision.
  • Iridium alloys are used to make electrical contact points in spark plugs.
  • Iridium is used to make aircraft engines due to its high resistant to corrosion and heat.
  • Iridium radioactive isotope, iridium-192 is used in making energy generators.

Health Hazards

Indium is a highly flammable metal. However, it is not considered very toxic. Exposure to indium can lead to minor irritation of eyes and ingestion can lead to slight stomach disorder.

Isotopes of Iridium

Iridium has only two naturally occurring isotopes, iridium-191 and iridium-193 [5]. And has around 34 artificially occurring isotopes, that range in mass number from 164 to 199. The most stable radioactive artificial isotope is irdium-192 (73 days).

REFERENCES

[1]. Weeks, M. E. (1968). Discovery of the Elements (7th ed.). Journal of Chemical Education. pp. 414–418. ISBN 0-8486-8579-2. OCLC 23991202.

[2]. Iridium” (PDF). Human Health Fact Sheet. Argonne National Laboratory. 2005. Archived from the original (PDF) on March 4, 2012. Retrieved 2008-09-20.

[3]. Emsley, J. (2003). “Iridium”. Nature’s Building Blocks: An A–Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 201–204. ISBN 0-19-850340-7.

[4]. Lagowski, J. J., ed. (2004). Chemistry Foundations and Applications. 2. Thomson Gale. pp. 250–251. ISBN 0028657233.

[5]. Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A. H. (2003). “The NUBASE Evaluation of Nuclear and Decay Properties”. Nuclear Physics A. Atomic Mass Data Center. 729: 3–128. Bibcode:2003NuPhA.729….3A. doi:10.1016/j.nuclphysa.2003.11.001

Hafnium

Hafnium was discovered in 1923 as a novel metal by Hevesy and Coster. In nature, it exists in combination with zirconium and its alloys have high refractory properties.

History and Discovery

Hafnium was discovered as a novel element by Georg von Hevesy and Dirk Coster in 1923. They analyzed the mineral zircon through X-ray spectroscopic analysis and found the novel element Hafnium. However, its presence was predicted by Dmitri Mendeleev (1869).  The name hafnium has been derived from Latin word Hafnia, that was the name of Copenhagen, the home town of Niels Bohr and the discoverers of hafnium. Bohr’s theory predicted that a novel element was associated with zirconium [1].

Hafnium

Periodic Table ClassificationGroup 4
Period 6
State at 20CSolid
ColorSteel gray
Electron Configuration[Xe] 4f14 5d2 6s2
Electron Number72
Proton Number72
Electron Shell2, 8, 18, 32, 10, 2
Density13.31 g.cm-3 at 20°C
Atomic number72
Atomic Mass178.49 g.mol -1
Electronegativity according to Pauling1.3

Occurrence

Hafnium is not very abundant element and is found in a concentration of about 5.8 ppm in the Earth’s crust. Hafnium does not exist in free metallic form in nature. It is found in combined mineral with zirconium, including thortveitite, alvite [(Hf, Th, Zr) SiO4 H2O] and zircon (ZrSiO4). Hafnium is obtained as byproduct during the refinement of zirconium. However, the separation of hafnium and zirconium is extremely difficult as the two elements closely resemble reach other. Large mineral deposits of hafnium and zirconium have been found in Malawi and Brazil and Australia [2].

Physical Characteristics

Hafnium is a greyish-silver lustrous metal.  It is a transition metal and resembles zirconium in its chemical properties, as both have equal number of valence electrons. It is ductile and is resistant to corrosion. Hafnium is denser than zirconium.

Chemical Characteristics

Hafnium is resistant to attacks by concentrated alkalis. It reacts with halogens to form hafnium tetrahalides. When exposed to air, hafnium forms a protective layer on its surface that is prves to be protective against corrosion. Hafnium also react with carbon, oxygen, sulfur and nitrogen, at elevated temperatures. Hafnium nitride is characterized as the most refractory of all nitrides of metals, and it has melting point of as high as 3310°C. So, it can withstand high temperatures. It has significant nuclear properties as it can absorb high thermal neutrons, whereas, zirconium is transparent to neutrons. The common oxidation state of hafnium is +4. Compounds of hafnium and zirconium have similar attributes.

Significance and Uses

  • Hafnium is widely used to make neutron absorbing rods (control rods) in nuclear reactors.
  • Hafnium is used in incandescent lamps, as it can scavenge nitrogen and oxygen.
  • Hafnium dioxide is being considered as an ideal candidate for use as insulators in High-K gates used in integrated circuits.
  • Hafnium nuclear isomer, Hf-178-ms has potential for use in nuclear energy generation projects and nuclear war heads.
  • Hafnium is used to make electrodes and filaments.
  • Hafnium is used to make various superalloys, with tungsten, niobium and titanium that are used in various significant applications.
  • Hafnium and its carbides are widely used as construction materials that are exposed to very high temperature.
  • Hafnium alloys are used in making simulation of supercomputer that can withstand temperatures as high as 4400 K [3].

Health Hazards

Hafnium metal is non-toxic. However, exposure of various compounds and salts of hafnium are considered potentially dangerous. Hafnium in powdered or fine divided form is considered hazardous and needs to be handled with care. As powdered hafnium can spontaneously ignite when exposed to air (pyrophoric).

Isotopes of Hafnium

Hafnium has 34 isotopes, with mass number ranging from 153 to 186 [3]. There are five stable isotopes of hafnium, hafnium-176 to 180. The most stable radioactive isotope is hafnium-174, that has a half-life of 1015 years [4].

REFERENCES

[1]. Bob Weintraub, George De Hevesy (1885 1966) (pdf document)

[2]. Dubbo Zirconia Project Fact Sheet” (PDF). Alkane Resources Limited. June 2007. Archived from the original (PDF) on 2008-02-28. Retrieved 2008-09-10.

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

[4]. EnvironmentalChemistry.com. “Hafnium Nuclides / Isotopes”. Periodic Table of Elements. J.K. Barbalace. Retrieved 2008-09-10.

Francium

Francium was discovered in 1939. It is very unstable alkali metal and considered the second rarest element in the earth crust.

History and Discovery

Francium was discovered by Marguerite Perey in 1939, who was studying the decay of actinium-227 by negative beta decay to an isotope of thorium and by alpha emission into an isotope of Francium-223, which was known as actinium.  Dmitri Mendeleev predicted the existence of element based on the gap in the periodic table in 1870. Perey suggested the name francium after France and this name was adopted by the IUPAC (International Union of Pure and Applied Chemistry) in 1949. Francium is the last natural element to be discovered [1].

Francium

Periodic Table ClassificationGroup 1
Period 7
State at 20CSolid (predicted)
ColorSilver-gray-metallic (presumed)
Electron Configuration[Rn] 7s1
Electron Number87
Proton Number87
Electron Shell2, 8, 18, 32, 18, 8, 1
Density0.00 g.cm-3 at 20°C
Atomic number87
Atomic Mass223 g.mol -1
Electronegativity according to Pauling>0.79

Occurrence

Francium is formed by radioactive decay of actinium, and artificially made by bombarding thorium with protons. It is naturally present in uranium and consider the second rarest element in the earth crust. It exists in short-lived radioactive forms and cannot be isolated in pure stable form. It is estimated that less than 30 grams of francium occur at any time in the earth crust.

Physical Characteristics

Francium is the shiny metal in its pure state and exist in liquid form at room temperature rather than a solid. Francium belongs to alkali group of the periodic table so its physical properties are similar with alkali group elements. Its melting point is about 27oC and its boiling point is 677oC, but both have uncertainty due to high radioactivity and is extremely rare in nature. Francium is heaviest known metal of alkali group. Its atomic number is 87 and atomic mass is 223 [2].

Chemical Characteristics

Francium chemical properties are similar with caesium. It has slightly higher ionization energy and electron affinity than caesium. It is the least electronegative element so it is chemically reactive alkali metal. And readily loses it outer shell to become Nobel element. Like alkali metals it is readily oxidized in air and vigorously react with water. It exit in +1 oxidation state. It has slightly higher ionization energy than cesium. Nearly all francium salts are water soluble.

Significance and Uses

  • There are no commercial applications due to its instability and rarity in nature.
  • Francium has been used in research purpose only [3].

Health Hazards

Francium has no known biological role in human life. Its toxicity is just due to its radioactivity, that can cause damage to cells and nuclear material.

Isotopes of Francium

The longest-lived isotope of francium is Fr-223, which has a half-life of only 22 minutes. Thirty four artificial isotopes with atomic masses from 199 to 232 because natural isotope of francium cannot be concentrated. All isotopes decay into astatine, radium or radon.

REFERENCES

[1]. https://www.britannica.com/science/francium

[2]. http://www.newworldencyclopedia.org/entry/Francium

[3]. Winter, Mark. “Uses”. Francium. The University of Sheffield. Retrieved March 25, 2007.

Cesium

Cesium was discovered in 1860. It is outstanding in keeping time with precision, so it is used in atomic clocks. It forms alloys with alkali metals, gold and mercury.

History and Discovery

Cesium is considered the first element who was discovered spectroscopically in 1860 by Robert Bunsen and Gustav Kirchhoff. They also derived its name from Latin caesius ‘’sky-blue’’ due to the formation of unique blue lines in the emission spectrum. [1]

Cesium

Periodic Table ClassificationGroup 1
Period 6
State at 20CSolid
ColorPale gold
Electron Configuration[Xe] 6s1
Electron Number55
Proton Number55
Electron Shell2, 8, 18, 18, 8, 1
Density1.87 g.cm-3 at 20°C
Atomic number55
Atomic Mass132.91 g.mol -1
Electronegativity according to Pauling0.79

Occurrence

Cesium occurs in minute quantity in earth crust in the form of minerals like pollucite (zeolite mineral cesium ore). It is mostly present with rubidium in nature and other alkali metals. The abundance of cesium on the earth crust is about 3 part per million and it is the 50th most common element in the earth crust [2].

Physical Characteristics

Cesium is a silvery-gold metallic element. It is an extremely soft metal. Cesium is one of four elements who exist in liquid form at or near room temperature. In periodic table it belongs to alkaline elements. Its physical properties are similar with rubidium and potassium. In the presence of mineral oil it loses its metallic luster. It has the melting point of 28.5oC and also has a low boiling point 641oC. Its golden color is due to decreasing frequency of light that is why it partially absorbs violet light while other colors are reflected hence it appears yellowish or golden in color. Cesium atomic number is 55 and its atomic mass is 132.90 g/mol.

Chemical Characteristics

Cesium is very reactive and pyrophoric (ignites spontaneously in air). It reacts with water vigorously and explosively, even at low temperatures. Cesium resembles rubidium in its chemical characteristics [3]. Cesium can be handled only under an inert gas, such as argon. It is exit in +1 oxidation state. In compounds it is present as Cs+ and binds ionically with anions. Its salts are usually colorless unless anion itself is colored. Double salts are less soluble but others like phosphate, acetate, carbonate are water soluble. Salts are hygroscopic in nature (attracting and holding water from surrounding). It is difficult to handle cesium because it reacts spontaneously and react with air. Cesium burns readily to form superoxide. Cesium hydroxides is a strong base which can attack glass. It react with halogens and forms fluoride, chloride, bromide and iodide.

Significance and Uses

  • Cesium is used in vacuum tubes as a “getter” to clean the traces of oxygen and other gases when sealed.
  • Cesium compounds with chlorides are used in photoelectric cells.
  • Cesium is used in industries as a catalyst promoter.
  • Cesium nitrate is used to make optical glasses.
  • Cesium is widely used in the production of electricity, electronics and in chemistry.
  • Cesium is also used in the manufacturing of infrared lamps.
  • Cesium is widely used in clocks. And it also used to determine the fundamental unit of time.
  • Cesium salts are used in water treatment and making mineral water.
  • Cesium vapor is used in making magnetometers.
  • Cesium is used in molecular biology for density gradient ultracentrifugation.
  • It is used in the catalytic conversion of sulfur dioxide into sulfur trioxide.
  • Cesiums-137 is radioactive isotope used as a gamma –emitter in various industrial application. It is used in medical field to treat various types of cancer.
  • Cesium and rubidium are used as a carbonate to manufacture high quality glass because they reduce electrical conductivity and improve stability.
  • It is used as cesium formate (anion derived from formic acid) for drilling fluids.

Health Hazards

Due to its high reactivity, cesium is considered as a hazardous metal. People who work in nuclear power station may be exposed to cesium, otherwise there is no health risk associated with cesium. People can experience cell damage due to its radiation effects and may suffer from nausea, vomiting, diarrhea and bleeding.

Isotopes of Cesium

It has thirty-nine known isotopes, having atomic masses ranging from 112 to 151. The only stable isotope of cesium is 133 Cs. Cs-135 has very long half-life of about 2.3 million years.

REFERENCES

[1]. https://www.britannica.com/science/cesium

[2]. Turekian, K. K.; Wedepohl, K. H. (1961). “Distribution of the elements in some major units of the Earth’s crust”. Geological Society of America Bulletin72(2): 175–192.

[3]. Greenwood, N. N.; Earnshaw, A. (1984). Chemistry of the Elements. Oxford, UK: Pergamon Press. ISBN 978-0-08-022057-4.

Cadmium

Cadmium is toxic metal and its discovery is credited to two scientist, Karl Smuel and Friedrich Strohmeyer, who simultaneously reported its discovery in 1817. Cadmium based pigments and batteries are widely sed since its discovery.

History and Discovery

Cadmium was discovered as an impurity from the ore of zinc carbonate by Friedrich Strohmeyer in 1817 (Germany). Discovery of cadmium is also credited to Karl Smuel who simultaneously discovered cadmium in zinc ore (zinc carbonate) termed as calamine [1]. Both the scientist belonged to Germany, and for many decades, Germany remained the prime producer of cadmium. The name cadmium has been derived from cadmia (Latin) and kadmeia (Greek) that means zinc carbonate.  In 1950s, cadmium was widely used in making yellow, orange and red pigments and later as coating agent on the world’s renowned plastic polymer, PVC. But in 1980s, the use of cadmium was greatly reduced due to concerns related to its toxicity and its environmental and health hazards.

Cadmium

Periodic Table ClassificationGroup 12
Period 5
State at 20CSolid
ColorSilvery bluish-gray metallic
Electron Configuration[Kr] 4d10 5s2
Electron Number48
Proton Number48
Electron Shell2, 8, 18, 18, 2
Density8.65 g.cm-3 at 20°C
Atomic number48
Atomic Mass112.41 g.mol -1
Electronegativity according to Pauling1.69

Occurrence

Cadmium is a rare metal. The concentration of cadmium on the Earth is around 0.5 ppm (parts per million). Mostly it is present in the form of ores of zinc and sulfide. The sulfide ore of cadmium is termed as greenockite (CdS). Currently, cadmium is obtained from the mining, smelting and purification of ores of zinc sulfide, and copper sulfide. Elemental form of cadmium has been found in Siberia.  The leading producers of cadmium in the world are Japan, China and South Korea and North America.

Physical Characteristics

Cadmium is whitish blue transition metal. It is soft and malleable and can be cut with a knife. Cadmium is a divalent metal and is insoluble in water. Cadmium is resistant to fire and is inflammable but is flammable in powdered form. Cadmium is an outstanding conductor of electricity. It is resistant to corrosion. Cadmium metal is unreactive with water [2].

Chemical Characteristics

Cadmium is not highly reactive. However, when exposed to air, cadmium undergoes tarnishing. When burned in the presence of air, if forms oxide (cadmium oxide CdO). Cadmium is not soluble in alkalis (such as sodium hydroxide) but is dissolved in acids (such as sulfuric acid). With halogens, cadmium forms compounds with fluorine, iodine and bromine: CdF2, CdI2 and CdBr2 [3].

Significance and Uses

  • Cadmium is widely used in the production of cadmium batteries, such as rechargeable cadmium nickel batteries.
  • Cadmium is used as an electroplating agent to protect aircrafts etc. from corrosion.
  • It is used in nuclear reactors as control rods.
  • Cadmium is used to make lasers and UV lamps.
  • Cadmium is used for making bearings and in alloys used in making bearing due to its resistance to high fatigue and low coefficient of friction.
  • Various salts of cadmium are used in making pigments, such as cadmium selenide is termed as cadmium red as it is used to make red pigment and cadmium sulfide is used to make yellow pigment.

Health Hazards

Cadmium is a highly toxic compound. It is considered as a carcinogenic (cancer causing) element. If inhaled or ingested, cadmium cause toxicity in various organs of the body, such including reproductive, gastrointestinal system, renal and cardiovascular system. Cadmium toxicity is considered as an occupational hazard and according to an estimate, around 300,000 individuals working in various industries are exposed to cadmium toxicity. For instance, personals working in metal smelting and refining plants, and manufacturing of plastic, solar panels and batteries [4]. Cadmium contamination from soil can accumulate in certain crops, such as rice and tobacco plants, which can cause toxicity in humans when consumed [5].

Isotopes of Cadmium

Cadmium has more than 30 isotopes. There are 8 naturally occurring isotopes in the cadmium element. Two natural isotopes are radioactive, cadmium-113 and cadmium-116, while stable isotopes include cadmium-114, cadmium-108 and cadmium-106, cadmium-110, cadmium-112 and cadmium-111. The most abundant stable isotope is cadmium-114 [2].

REFERENCES

[1]. Friedrich Stromeyer, Annals of Philosophy, edited by Thomas Thomson, Volume XIII, 1819, Robert Baldwin, p108

[2]. https://www.chemicool.com/elements/cadmium.html

[3]. https://www.webelements.com/cadmium/chemistry.html

[4] https://www.osha.gov/SLTC/cadmium/

[5]. Alireza Pourkhabbaz, Hamidreza Pourkhabbaz Investigation of Toxic Metals in the Tobacco of Different Iranian Cigarette Brands and Related Health Issues, Iran J Basic Med Sci. 2012 Jan-Feb; 15(1): 636–644. PMC 3586865

Boron

Boron is a metalloid and was discovered by Joseph L. Gay-Lussac and L. J. Thénard in 1808. It is chemically unreactive and is the second hardest element on earth.

History and Discovery

Boron is an ancient metal and have been known to human civilization since thousands of years. Its compound, sodium tetraborate that is commonly known as borax have been used in the manufacturing of glass in very early time. Boron was discovered by Joseph L. Gay-Lussac and L. J. Thénard in 1808 that was around 60% pure. The pure form of boron was isolate by Henri Moissan (French chemist) in 1892 and then in 1909, almost 100% pure boron was isolated by Ezekiel Weintraub. The name borax has been originated from buraq (Arabic) and burah (Persian) meaning “white” [1].

Boron

Periodic Table ClassificationGroup 13
Period 2
State at 20CSolid
ColorBlack-brown
Electron Configuration[He] 2s2 2p1
Electron Number5
Proton Number5
Electron Shell2, 3
Density2.34 g.cm-3 at 20°C
Atomic number5
Atomic Mass10.81 g.mol -1
Electronegativity according to Pauling2.04

Occurrence

Boron has an average abundance on Earth and is present in a concentration of 10 ppm in the Earth’s crust. In nature, boron does not exist in free or elemental form but in the form of compounds. Boron is present embedded in sedimentary rocks and sediments. It is also present in volcanic spring waters. The primary sources of boron are borax ore ((Na 2 B 4 O 7), kernite (Na2B4O6(OH)2.3H2O) and colemanite (CaB3O4(OH)4.H2O). These ores or minerals are present in desert areas. The largest producers of boron are USA and Turkey [2].

Physical Characteristics

Boron is a hard metal and is considered the second hardest element in the world. Boron has a unique nature, as it has characteristics that are intermediate between non-metals and metals and thus considered as a metalloid. Boron is quite distinct element in its group, as all other members of Group 13 are true metals. Boron exists in various allotropic forms (different forms of same elements that have different chemical and physical properties). Due to these allotropic forms, boron can exist as red crystals, black crystals or brown powder. Boron, in all allotropic forms have a high boiling point. Boron is a heat resistant element. It has one of the highest boiling points. Boron can absorb neutrons with great efficiency. At room temperature, boron is an insulator, but its electrical conductivity increases with an increase in temperature [3].

Chemical Characteristics

Amorphous form of boron is reactive. In crystalline form, boron is quite unreactive. It makes stable covalent bonds with other compounds and does not forms ionic bonds. Boron combines with air to form boron trioxide, which acts a protective layer on the surface of boron and protects the metal from further oxidation. Born in powdered form reacts with hot sulfuric acid and nitric acid and dissolves in molten metals [4].

Significance and Uses

  • Boron is widely used in the making of glass, glass fiber, borosilicate fiber and ceramic products.
  • Boric acid is used as an antiseptic to treat mild infections.
  • Boron is also compound of fertilizers.
  • Boron is used in the manufacturing of various alloys to impart desirable characteristics. For instance, the strongest magnets are made from alloys of boron with iron and neodymium. Various electronic devices use these magnets, such as headphones, loudspeakers and particle accelerators.
  • Boron coating and alloys are widely used a flame retardant (material that prevent burning of other material).
  • Boron is used as doping agent in making silicon semiconductors used in electronic devices.
  • It is also used an active component of herbicides and insecticides.
  • Boron is a major component of ceramic equipment used for carrying out high-temperatures tasks.
  • Boron is used in making bullet proof vests, vehicles and armor trucks.
  • Boron nitride and boron carbide as used in making refractory materials such as oven, incinerators.

Health Hazards

Boron is non-toxic. Boron plays various roles in the bodies of plants and animals as micronutrient. In plants, boron plays important role in regulation of certain proteins and it aids the plants in uptake of water from soil. Boron deficiency can lead to crumpled and twisted leaves in plants. In animals, boron deficiency can lead to bone defects as boron plays important role in maintain healthy bones. The daily recommended dose of boron in humans in around 3 milligrams. Various nuts, beans, green vegetables and fruits help fulfill the required boron need of the body [5].

Isotopes of Boron

Boron has eleven isotopes, with mass number ranging from seven to seventeen. There are two isotopes in naturally occurring boron, boron-10 and boron-11. Boron-10 is widely used in nuclear reactors for capturing and absorbing of neutrons.

REFERENCES

[1]. Alaa S. Abd-El-Aziz, Macromolecules Containing Metal and Metal-Like Elements Volume 8 Boron-Containing Polymers., (2007) p2. Wiley-Interscience

[2]. “U.S. Borax Boron Mine”. The Center for Land Use Interpretation, Ludb.clui.org. Retrieved 2013-04-26.

[3]. http://www.chemistryexplained.com/elements/A-C/Boron.html

[4] Laubengayer, A. W.; Hurd, D. T.; Newkirk, A. E.; Hoard, J. L. (1943). “Boron. I. Preparation and Properties of Pure Crystalline Boron”. Journal of the American Chemical Society. 65 (10): 1924–1931. doi:10.1021/ja01250a036.

[5]. Pizzorno, L (Aug 2015). “Nothing boring about boron”. Integrative Medicine. 14 (4): 35&ndash, 48. PMC 4712861. PMID 26770156.

 

 

Aluminum

Aluminum is an ancient metal and has with diverse range of uses. It was discovered in 1824 and its light weight, high electrical conductivity and high resistant to corrosion has make it an industrially attractive metal.

History and Discovery

The history of alum dates to Greek historian in 5 th century BCE, and over the centuries it was used for various purposes, including defense fabric, dyeing mordant etc. It was identified as a distinct salt of an element in 1530 by Paracelsus. Aluminum was formally discovered as a new metal by Hans Christian Orsted in 1824 [1]. It was named by Humphry Davy in 1812. The word aluminum has been derived from Latin word that means bitter salt.

Aluminum

Periodic Table ClassificationGroup 13
Period 3
State at 20CSolid
ColorSilvery gray metallic
Electron Configuration[Ne] 3s2 3p1
Electron Number13
Proton Number13
Electron Shell2, 8, 3
Density2.7 g.cm-3 at 20°C
Atomic number13
Atomic Mass26.98 g.mol -1
Electronegativity according to Pauling1.61

Occurrence

Aluminum is an abundant metal and is characterized as the third most abundant element in the Earth’s crust (8% by mass). Aluminum is also quite abundant in space and is ranked 12 th among all elements with an abundance of about 3.15 ppm. Aluminum does not occur in native metallic form. And due to its high reactivity, aluminum is found in combined form in more than 250 different minerals [2]. It primarily exists in form of ores and the most common ore of aluminum is bauxite. The largest producers of aluminum in the world are China, Russia, Bahrain, and South Africa.

Physical Characteristics

Aluminum is a greyish silver metal. It is soft, and extremely malleable and ductile. Aluminum is nonmagnetic. It has very low density (2.7 g/cm -3 ). Aluminum is resistant to corrosion and can withstand environmental exposure for significantly long time periods. It is non-absorptive. And aluminum is highly conductive of electricity and is relatively cheaper than copper.

Chemical Characteristics

Aluminum is a reactive metal. It is readily oxidized when exposed to air. The most common oxidation state of aluminum is +3. Aluminum reacts with oxygen and sulfur to form oxides and sulfates, which have various industrial applications. It readily reacts with acids and bases.

Significance and Uses

  • Aluminum cans for packaging of food items and soft drinks have been widely used since 1958. Aluminum foils are widely used all over the world.
    Aluminum alloys are widely used in aerospace industry, for making space shuttles, satellites etc.
  • Aluminum is used in the manufacturing of cars, trucks, bicycles and marine vessels.
  • Aluminum is widely used construction and building material, such as doors, building wire, windows and roofing.
  • Aluminum is widely used in making of cooking utensils, furniture as well as house hold wiring.
  • Aluminum is widely used in making motors, capacitors, generators and transformers.
  • It is used as a catalyst in various industrial processes, for example, in formation of sulfur from hydrogen sulfide.
  • Aluminum is used as a common drying agent.
  • Aluminum phosphate is used in manufacturing of various cosmetic products, dental cement and paints.
  • Aluminum is used as an immune booster in various vaccine [3].

Health Hazards

Aluminum is not toxic. In most cases, it is well tolerated if ingested or inhaled by humans or plants. However, very rare evidence of aluminum toxicity is related to vitamin D deficiency, anemia and renal damage. Inhalation of powdered welding fumes of aluminum can lead to fibrosis of the lungs [4]. In environment, aluminum can affect the soil fertility as it reacts with phosphate and makes it less available for the plants [5].

Isotopes of Aluminum

Aluminum has only one stable isotope, aluminum-27. Among the radioactive isotopes, the most stable is aluminum-26 and have a half life of about 720,000 years.

REFERENCES

[1]. Royal Danish Academy of Sciences and Letters (1827). Det Kongelige Danske Videnskabernes Selskabs philosophiske og historiske afhandlinger [The philosophical and historical dissertations of the Royal Danish Science Society] (in Danish). Popp. pp. XXV–XXVI.

[2]. Shakhashiri, B. Z. (17 March 2008). “Chemical of the Week: Aluminum” (PDF). SciFun.org. University of Wisconsin. Archived from the original (PDF) on 9 May 2012. Retrieved 4 March 2012.

[3]. Singh, Manmohan (3 August 2007). Vaccine Adjuvants and Delivery Systems. John Wiley & Sons. pp. 81–109. ISBN 9780-470-13492-4.

[4]. al-Masalkhi, A.; Walton, S. P. (1994). “Pulmonary fibrosis and occupational exposure to aluminum”. The Journal of the Kentucky Medical Association. 92 (2): 59–61. ISSN 0023-0294. PMID 8163901

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