Chemical Properties of Zinc

The compounds and alloys of zinc were known to mankind since ancient times. However, the properties of the metal were first described by Paracelsus Aracelsus, a Swiss-born German alchemist in the early part of the 16th century.

He had given the metal its name 'zink', which is believed to be derived from a German word 'zinke' which means pointed as zinc crystals look like sharp needles. However, he was not aware of the exact composition of the metal.

For this reason, many people feel that the credit for discovering zinc should go to German chemist, Andreas Marggraf as he isolated the pure form of the metal in 1746.

In its pure form, zinc metal is lustrous, bluish gray in color. It is mostly extracted from its ore, zinc blende or sphalerite, which is a sulfide form of zinc. This ore is abundantly available on the surface of the earth. Large deposits of this ore are found in various parts of Asia, Australia and the United States.

In chemistry, the element zinc is considered as a transition metal and is represented with the symbol Zn. Like other transition metals, it is a d-block element in the periodic table. Here, it is placed in the fourth period and twelfth group. It is in the same group as cadmium and mercury.

The chemical properties exhibited by an element are governed by the properties of its atoms. Let us take a look at some of the atomic properties of zinc:

• Atomic Number: 30
• Atomic Weight: 65.37
• Electrons per Shell: 2, 8, 18, 2
• Atomic Radius: 134 pm
• Oxidation State: +2

Some important points about chemical properties of zinc metal are as follows:

• As you can see from the electronic configuration of zinc, it is bivalent in nature as it has two electrons in its outermost shell or the valence shell.

• Its oxidation state is +2 and thus, it acts as a strong reducing agent where it is the donor of these two electrons to form an ion. During a chemical reaction, it has a tendency to form a covalent bond.

• The size of zinc ion is same as that of magnesium and has an oxidation of +2. For this reason, chemical properties of zinc and magnesium have got lots of similarities.

• This metal does not react with atmospheric air in absence of moisture. However, when it comes in contact with the moist air, then its surface gets tarnished easily. This is because its outer layer reacts with carbon dioxide present in the air to form zinc carbonate (Zn₅(OH)₆(CO₃)₂). 

This thin and tarnished coat is referred to as passivation layer and is formed to provide protection to its underlying surface from air and water.

• When pure zinc metal is burnt in air, then it gives out a bright bluish green flame and gaseous form of zinc oxide is obtained in the process.

• At room temperature, pure form of zinc usually does not react with weak or dilute acids because of the presence of passivation layer on its surface. However, if it comes in contact with concentrated form of strong acids like hydrochloric acid, then it undergoes a slow chemical reaction and hydrogen gas is released. 

The acids first dissolve the protective layer on zinc and then the reaction with the metal starts. However, these acids can corrode zinc faster, if it has trace amounts of nickel salts in them.

• At normal room temperature, zinc does not react with gaseous form of halogens like chlorine or fluorine. If it is exposed to these gases at a higher temperature, then zinc halides are formed.

• When zinc salts are dissolved in water, then they undergo hydrolysis to form zinc hydroxide (Zn(OH)₂), which is insoluble in water and forms precipitates. Moreover, this hydroxide is amphoteric in nature, which means that it has both acidic and basic properties.

All these properties are utilized in various uses and applications of zinc. One key application of zinc is in galvanizing metals. In the galvanization process, iron and steel are coated with a layer of zinc to protect the surface from corrosion or rusting.

It is also used in batteries and helps to remove water impurities. Due to all these important usage, zinc is considered as one of the most valuable metals.