Question

Which of the given elements a, b, c, d and e with atomic number 2, 3, 7, 10 and 30 respectively belongs to the same period -

Answer 1

The electronic configuration of the elements are-
a-2
b-2.1
c-2.5
d-2.8
e-2.18.8.2

b,c,d belong to same period as they have same number of shells.