Question

Identify the pair of elements from among the following which have the same number of valence electrons.

• A. Cl, Ar
• B. C, Ge
• C. Na, Ca
• D. K, Mg

Answer 1

The correct option is B

C, Ge

Electrons present in the outermost shell of an atom are called valence electrons. Electronic configurations for the given elements are as follows:
Cl(17) – 2,8,7 $\to$ valence electrons : 7
Ar(18) – 2,8,8$\to$ valence electrons : 8
C(14) – 2,8,4 $\to$ valence electrons : 4
Ge(32) – 2,8,18,4 $\to$ valence electrons : 4
Na(11) – 2,8,1 $\to$ valence electrons : 1
Ca(20) – 2,8,8,2 $\to$ valence electrons : 2
K(19) – 2,8,8,1 $\to$ valence electrons : 1
Mg(12) – 2,8,2 $\to$ valence electrons : 2
So, it is obvious that the pair of elements with same no: of valence electrons is (C, Ge)