Question

Why chemical reactivity decreases an d then increase on moving left to right in a period?

Answer 1

HEY MATE HERE'S YOUR ANSWER;

It becomes more and more difficult to lose electrons and consequently the reactivity of the metals decreases as you go from left to right across the periodic table. As you go down the periodic table, the nuclear charge increases but so does the number of shielding electrons.

The reactivity in metals increases on going down the group, ... The chemical reactivity of non-metals decreases ongoing down the group as it depends on the tendency to gain electrons. Across a period. On moving from left to right in a period, the chemical reactivity of elements first decreases and then increases.