Elements with atomic numbers 17 and 20 form compounds with hydrogen. Write the formula of these two compounds and compare their chemical behaviour in water.

Explanation

Elements with atomic number `17` is chlorine and `20` is calcium. They form compounds with hydrogen :
`I .HCl,ii CaH_(2)`
Hydrogen forms molecular hydride with `p`-block elements. `HCl` is a compound which is covalent bonded and easily dissolved in water. while `CaH_(2)` is salt-like hydride and it gets easily hydrolysed and produces `H^(ɵ)` ion which shows their ionic nature.