Write the formula of calcium chloride . Also write the elements present in it.

Explanation

Corrosion: The process of slowly.eating up of the metals due to attack of atmospheric gases (such as oxygen, carbon dioxide, hydrogen sulphide, water vapour etc.) on the surface of metals is called corrosion.
The most common example of corrosion is rusting, i.e., corrosion of iron. When an iron article remains exposed to moist air for along time, its surface is covered with a brown, flaky (non-sticky) substance called rust. Rust is mainly hydrated ferric oxide (`Fe_2O_3.x H_2O`). It is formed due to attack of oxygen,gas and water vapour present in the air on the surface of iron.
`underset("Iron")(2Fe(s)) + underset("Oxygen")(3//2 O_2 (g)) + underset("Moisture")(xH_2O (l)) rarr underset("oxide (Rust)")underset("Hydrated ferric")(Fe_2O_3 . xH_2O (s))`
Similarly, copper objects lose their luster or shine after some time. The surface of these objects acquires a green coating of basic copper carbonate, `CuCO_3. Cu(OH)_2` when exposed to air. This is due to attack of `O_2, CO_2` and, water vapour present in the air on the surface of copper.
`underset("Copper")(2Cu(s))+ underset("From moist air")(CO_2(g) + O_2(g)) + H_2O(l) rarr underset("(Green)")underset("Basic copper carbonate")(CuCO_3.Cu(OH)_2)`
Likewise, the surface of silver metal gets tarnished (i.e. loses lustre and becomes dull) on exposure to air: This is due to the formation of a coating of black silver sulphide (`Ag_2S`) on its surface by the action of `H_2S` gas present in the air.
`underset("Silver")(2Ag (s)) + underset("(From air) (Black)")underset("Hydrogen sulphide")(H_2S(g)) rarr underset("Silver sulphide")(Ag_2S (s))`