Question

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

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

Answer 1

The correct option is A 2.4 $N_A$

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

0.3mol =$0.3\times N_A$ ions

Number of valence electrons present in one mole of $N^{3-}=8$

Valence electrons present in 0.3 moles of $N^{3-}$ =$8\times 0.3\times N_{A}electrons$

=2.4 $N_A$