Question

The elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively. Which pair of elements belongs to the same group?

• A. A and B
• B. B and D
• C. A and C
• D. D and E

Answer 1

Answer: (C)

A and C

Let us take a look at the electronic configurations of the given elements,

A: (2, 7)
B: (2, 8, 1)
C: (2, 8, 7)
D: (2, 8, 2)
E: (2, 8, 3)

We can see that elements A and C both have 7 valence electrons. Thus, both the elements belong to the same group.

So, the correct option is $C$