Question

If an atom has two electrons in its outermost shell. Which among the following can be the atomic number of that atom?

• A. 10
• B. 11
• C. 12
• D. 13

Answer 1

The correct option is C

12

- The maximum number of electrons that can be accommodated in any shell is given by $2$$\times$${\text{n}}^2$, where n is the shell number. $$\begin{array}{ccc}\text{Shell}& \text{Shell number, n}& \text{Maximum number of electrons}\\ \text{K}& \text{1}& \text{2}\\ \text{L}& \text{2}& \text{8}\\ \text{M}& \text{3}& \text{18}\end{array}$$ - The electrons in the outermost shell are called valence elctrons.
$$\begin{array}{ccc}\text{Atomic number}& \text{Electronic configuration}& \text{Valence electrons}\\ \text{10}& \text{2,8}& \text{8}\\ \text{11}& \text{2,8,1}& \text{1}\\ \text{12}& \text{2,8,2}& \text{2}\\ \text{13}& \text{2,8,3}& \text{3}\end{array}$$ - Since, element having atomic number 12 has two valence electrons hence, it is the correct option.