Explain giving a reason, why:

(i) Metallic character decreases in a period.


(ii) Atomic size increases in a group.


(iii) Chemical reactivity first decreases and then increases in a period.

(i) As the effective nuclear charge acting on the valence shell increases across the period, the tendency to lose electrons decreases due to this metallic character decreases.

(ii) Atomic size increases in a group because new shells are being added as we go down the group. This increases the distance between the outermost shell and nucleus.


(iii) The reactivity of element depend upon their tendency to lose or gain electrons to complete their outermost shell, greater is the tendency to lose/gain electron greater is the reactivity


So, in a period first tendency to lose electron decreases so reactivity decreases and the tendency to gain electron increases so the reactivity increases.


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