Question

Predict the period and group number of elements whose outer electronic configuration is as:
(a) $n{s}^{2}n{p}^4(n=2)$
(b) $(n-1)d^{2}n{s}^2(n=5)$

Answer 1

a) 2s${}^2$ 2p${}^4$.

Here n=2 so it belongs to the 2nd period. It contains '6' valence electrons. So it belongs to 6th group.

b) 4d${}^2$ 5s${}^2$

Here n=5 so it is 5th period element. It contains '2' valence electrons. So it is 2nd group element.