Zinc is a prehistoric metal and have been used as copper alloy since 3rd millennium BC. It is widely used today to make electrical batteries and for zinc electroplating.
History and Discovery
The history of zinc dates to around 3rd millennium BC, when it was used in the form of alloy with copper (brass). Traces of use of brass in various applications have been found in ancient civilizations of Iraq, Kalmykia, UAE, West Indies, Iran and Syria [1]. In the 9th century AD, a distillation process was developed in Rajasthan to obtain pure zinc. The commercial production of zinc started in the 12th century. Zinc was discovered in pure form in 1746 by German Chemist Andreas Sigismund Marggraf. And a detailed insight in the electrochemical properties of zinc was presented by Luigi Galvani and Alessandro Volta in 1800.Zinc was named as white snow by Alchemists, as it burned in air to form white compound. The word zinc has been derived from German word Zinke that means tooth.
Zinc
| Periodic Table Classification | Group 12 Period 4 |
|---|---|
| State at 20C | Solid |
| Color | Silver-gray |
| Electron Configuration | [Ar] 3d10 4s2 |
| Electron Number | 30 |
| Proton Number | 30 |
| Electron Shell | 2, 8, 18, 2 |
| Density | 7.13 g.cm-3 at 20°C |
| Atomic number | 30 |
| Atomic Mass | 65.39 g.mol -1 |
| Electronegativity according to Pauling | 1.65 |
Occurrence
Zinc is quite abundant element and is ranked as the 24th most abundant element in the Earth’s crust (around 75ppm). It is found in soil and sea water. Mostly, it is present in the form of ores and minerals of copper and lead. The most common ore of zinc is sphalerite (zinc sulfide) and contains around 60% of zinc [2]. It is also found in other minerals such as hemimorphite (zinc silicate), smithsonite (zinc carbonate) and wurtzite (zinc sulfide). Australia, USA and Iran and Canada are the largest producers of zinc in the world.
Physical Characteristics
Zinc is a whitish-blue shiny metal. It is hard and brittle at standard temperature. And gives a specific sound when bent like tin. It becomes malleable when temperature is increased from 100C to 150 [3]. The boiling and melting points of zinc are lower as compared to other members of the d-block elements and are 907°C and 419.5°C, respectively. Zinc is a good electrical conductor and have diamagnetic properties.
Chemical Characteristics
Zinc is a reactive metal. The surface of zinc metal is quickly tarnished as it reacts with the carbon dioxide present in the air and forms a layer of zinc carbonate. It is a strong reducing agent [4]. Zinc readily reacts with non-metals, acids and alkalis. In the presence of concentrated sulfuric acid, the upper passivating layer of zinc carbonate is dissolved and lead to the release of hydrogen gas. The most common oxidation state of zinc is +2. It burns with a greenish blue flame and forms zinc oxide.
Significance and Uses
- Zinc is widely used for plating that imparts corrosion resistant upper layer to various metals.
- Zinc is used to make various alloys, such as brass.
- Zinc is used in the manufacturing of batteries.
- Zinc compounds, such as zinc gluconate and zinc carbonate are used as dietary supplements.
- Zinc is used as the active compound in various antidandruff shampoos.
- Zinc sulfide is used to make luminescent dyes and paints.
Health Hazards
Zinc is considered as a biologically important element. It is required for the proper growth and development of human fetus. Deficiency of zinc in children lead to delayed or retarded growth. About two billion people in the world suffer from zinc deficiency that lead to various disorders and ailments [5].
Isotopes of Zinc
There are five stable isotopes of zinc, these include zinc-64, zinc-66, zinc-67, zinc68 and zinc-70. The most abundant natural isotope is zinc-64, which has an abundance of 48.63% [6]. It has a half life of around 4.3×1018 year, which is so high that it is considered almost stable. There are several dozen radioactive isotopes of zinc.
REFERENCES
[1]. Kharakwal, J. S. & Gurjar, L. K. (December 1, 2006). “Zinc and Brass in Archaeological Perspective”. Ancient Asia. 1: 139–159. doi:10.5334/aa.06112. Archived from the original on December 3, 2013.
[2]. Lehto 1968, p. 822
[3]. Heiserman 1992, p. 123
[4]. CRC 2006, pp. 8–29
[5]. Prasad, A. S. (2003). “Zinc deficiency : Has been known of for 40 years but ignored by global health organisations”. British Medical Journal. 326 (7386): 409–10. doi:10.1136/bmj.326.7386.409. PMC 1125304. PMID 12595353.
[6]. NNDC contributors (2008). Alejandro A. Sonzogni (Database Manager), ed. “Chart of Nuclides”. Upton (NY): National Nuclear Data Center, Brookhaven National Laboratory. Archived from the original on May 22, 2008. Retrieved September 13, 2008