Question

An element has electronic configuration
2, 8, 7
(i) What is the valency of this element
(ii) The element will show resemblance with which of the following elements ?
N(7), F(9), P(15), Ar(18), Ca(20)

Answer 1

I think outermost she'll has no electronic configuration

Answer 2

Chlorine (Cl)

Explanation:

Given electronic configuration is 2, 8, 7.

We infer: Atomic number is 17. Chlorine is the element.

(i) Valency of chlorine is 1.

Valence electron in chlorine is 7 and it needs to gain 1 electron from the outermost orbit to attain octet.

(ii) The element will show resemblance with other halogens which have 7 valence electrons in their outer shell. So it will resemble F (9), Fluorine.