Periodic change in electronic configuration is responsible for the physical and chemical properties of element. Justify this statement.

Explanation

(i) The electronic configuration of the elements changes periodically in a period and group as well.
(ii) We could find a pattern in the physical and chemical properties as we go down in a group or move across a period.
(iii) For example: The chemical reactivity is high at the beginning, lower at the middle and increases to a maximum at group 17 in a period.
(iv) The reactivity increases on moving down the group of alkali metals. But the reactivity decreases on moving down the group of halogens.
(v) Atomic radii increases down the group and decreases across the period.