reactivity series
 

Though Hydrogen is a nonmetal why it is placed in reactivity series of metals?

It is just for comparison, so you can get a better idea of how reactive the other metals are, if it will react with water, or if it is easily reduced by hydrogen, etc.

reactivity series
 

Thank you very much for the answer posted.

Remember that the arrangement of the elements in the periodic table is such that elements with similar properties fall in the same group. Although hydrogen is a nonmetal, it resembles the properties of group 1 elements. It forms a +1 charge.

because hydrogen is under group 1, that is also the reason why in nomenclature of ionic compounds and molecules, HCl can also be read as hydrogen chloride. H2S can be read as hydrogen sulfide instead of just dihydrogen monosulfide. It can follow the rules in the nomenclature of ionic compounds. Ionic compounds are usually composed of a metal and a nonmetal, specifically, a cation and an anion.