Question

If $N_A$ is Avogadro's number, then number of valence electrons in 4.2 g of nitride ion $\left(N^{3-}\right)$ is:

• A. 4.2 $N_A$
• B. 2.4 $N_A$
• C. 1.6 $N_A$
• D. 3.2 $N_A$

Answer 1

Answer: (B)

Number of moles $=\frac{4.2}{14}=0.3$ mol

$0.3$ mol $=0.3\times N_A$ ions.

$\Rightarrow 8\times 0.3\times N_A$ electrons (as each ion contains $5+3={8e}^{-}$)

$\Rightarrow 2.4N_A$ electrons

Hence, the correct option is A.