The periodic table consist of about 117 well known elements. The elements, represented by symbols, are built from atoms where an atom being the basic unit of an element which can participate in a chemical reaction. The elements are arranged in periodic table according to their atomic number. The periodic table was first described in 1800 when scientists realized that some of the elements looked and behaved alike. The year 1872 saw Meyer and Mendeleev arrange 60 elements in the periodic table. The arrangement was based on their properties as well as their increasing atomic mass (Wilson, 2018).
Today, the 117 elements are arranged in the periodic table based on the distribution of electrons in their valence shells or based on their increasing atomic properties. The arrangement of electrons in the valence shells capitalizes on the s and p orbitals which basically contains electrons that are involved in bonding. For instance, both Sulphur S ([Ne] 3s23p4) and Oxygen (O ([He] 2s22p4) have similar properties because they contain same numbers of electrons in the valence shells (s and p orbitals) (Wilson, 2018). This paper describes Zinc (Zn) as an element in the periodic table looking into its physical and chemical properties as well as its uses.
Discovery and uses of Zinc
Andreas Marggraf first described Zinc (Zn), as an element, in the year 1746. Prior to this, Zn had been known to the Greeks and Romans as early as 20 BC though they rarely used it. Before it was described as an element, Zn ores were used to make brass which is a mixture of Zn and copper.
Today, Zn has several uses ranging from industrial to biological uses. In the industries, Zn is used in galvanizing metals. For instance, it is used to galvanize iron in order to prevent it from rusting. It is also used to galvanize steel that has used in making car bodies, safety barriers, street lamp posts and suspension bridges. Large quantities of Zn are used in the production of die-castings that are important for hardware and electric industries as well as automobile. At times Zn is used as silver, nickel, and brass alloys. Many manufacturing industries use Zinc oxide to produce rubber, paint, pharmaceuticals, inks, plastics, electrical equipment and batteries among others (Wilson, 2018).
Biologically Zn is viewed as an essential mineral in living organisms. It forms the active sites in more than 20 metallo-enzymes. On average the human body contains about 2.5 grams of Zn with the daily consumption standing at 1.5 grams. Despite its importance in living organisms, it should be noted that high intake of Zn could result in cancer as Zinc being a heavy metal is known to be carcinogenic (Roohani et al., 2013).
In the periodic table, Zn is classified among the second group, second sub group elements. Zn has an atomic mass of 65.38 with an atomic number of 30 (Jensen, 2003). The outer shell of the element is made up of 4s2 with a constant oxidation state of 2+. Zn is further classified among transition metals in the periodic table. Other transition metals include copper, manganese, cadmium and chromium (Schnelker, and Marsden, 2017)
Physical properties of Zinc
The Royal Society of Chemistry (RSC) describes various physical properties of Zn as an element (Wilson, 2018). According to the RSC, the physical properties of Zn are described below.
It is a member of group 12, period 4 and block d elements in the periodic table
It has a density of 7.13 g/cm³
It appears as a bluish-white substance at room temperature
It has a low melting point as compared to other metals (420 °C).
Its malleability and elasticity increases upon heating to 100 °C
It boils at 906 °C in its simplest form.
Heating the metal to 200 °C results in change of the metal’s elasticity thus changing into a gray powder.
It has high heat conductivity as well as heat capacity
It has a relative atomic mass of 65.38
It has electron configuration of [Ar] 3d104s2
Zn has five isotope, 64Zn, 66Zn, 67Zn, 68Zn and 70Zn
Chemical properties of Zinc
The chemical properties of Zn are determined by its physical appearance. Below is a description of the key chemical properties of Zinc (Wilson, 2018; Schnelker, and Marsden, 2017)
Zn has +2 valence electrons that take part in its chemical reactions
Under ordinary conditions Zn undergoes a swift reaction with air to form zinc oxide (dark grey coating)
It also reacts with halogens, ammonium, oxygen, ammonia salts, acids, alkalis as well as weaker metals.
Being an amorphic metal, Zn do not react with nitrogen
The element reacts with alkalis to form complex compounds known as hydroxo-zincates
It reacts with concentrated acids in a slow reaction leading to the production of hydrogen gas
It does not react with halogens at room temperature, but when exposed to the halogens at higher temperatures it reacts with them to form zinc halides
It doesn’t react with weak or dilute acids at room temperature due to the presence of a surface passivation layer
Sulfur has a strong affinity for Zn and upon mixing and heating Zn and Sulfur powders, the two elements reacts violently
Zn burns with a blue flame to form zinc oxide
In conclusion, Zn is a group 12 metal with distinctive chemical a physical properties. It also gained different biological and industrial uses over time. Since its discovery, Zn has gained more uses at the global scene.
References
Jensen, W. B. (2003) ‘The place of zinc, cadmium, and mercury in the periodic table.’, Journal of Chemical Education, 80(8), pp. 952–961. doi: 10.1021/ed080p952.
Roohani, N. et al. (2013) ‘Zinc and its importance for human health: An integrative review’, Journal of research in medical sciences: the official journal of Isfahan University of Medical Sciences. doi: 23914218.
Schnelker, T. and Marsden, S. R. (2017). Chemistry of Zinc Retrieved on 12th October 2018 from https://chem.libretexts.org/Textbook_Maps/Inorganic_Chemistry/Supplemental_Modules _(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/3_d- Block_Elements/Group_12%3A_Transition_Metals/Chemistry_of_Zinc
Wilson, E. (2018). 'Periodic table elements.' Royal Society of Chemistry. Retrieved on 12th October 2018 from http://www.rsc.org/periodic-table/element/30/zinc
