The electronic configuration of 4 elements A, B, C and D is as given under:

CBSE Class 10 CBSE Class 10 Science
,
1

The electronic configuration of 4 elements A, B, C and D is as given under:
A-2,1
B-2,2
C-2,8,2
D-2
(a) Which amongst them belongs, to the same group ? Name it.
(b) Which amongst them belongs to the same period? Name it
© Which amongst them is inert ? Name it

2

(a) B and C, beryllium (Be) Smd magnesium (Mg) respectively belong to group 2.
(b) A and B, lithium (Li) and beryllium (Be) respectively belong to second period.
© D (Helium) is inert.