Question

The total number of valence electrons in 4.2 gm of ${N_3}^{-}$ ion is ($N_A$ is the Avogadro's number)

• A. 1.6 N_A
• B. 3.2 N_A
• C. 2.1N_A
• D. 4.2N_A

Answer 1

The correct option is

A

1.6 N_A

42g of ${N_3}^{-}$ ions have 16 $N_A$ valence electrons

4.2g of ${N_3}^{-}$ ion have $=\frac{16N_A}{42}\times 4.2=1.6N_A$.