Question

what is chemical reactivity ...?

and why does it first decrease and then increase as we move from left to right in a period?

and why does it increase in metals as we go down a grup and decrease in non metals as we go down a group?

Answer 1

ability of any element to take part in chemical reaction is called reactivity... In metal it increases bcoz they have more unpaired electron in the outermost orbital that helps to take part in reaction but non metal does not contain much unpaired electrons