Explain about the salient features of groups.

Explanation

(i)  Number of electrons in outermost shell: The number of electrons present in the outermost shells does not change on moving down in a group, i.e remains the same. Hence, the valency, also remains same within a group.
(ii) Number of shells: In going down a group the number of shells increases by one at can step and ultimately becomes equal to the period number to which the element belongs.
(iii) Valency: The valencies of all the elements of the same group are the same. The valency an element with respect to oxygen is same in a group.
(iv) Metallic character: The metallic character of the elements increases in moving to bottom in a group