Question

the total no of valence electrons in 4.2 g of N3- ion is

Answer 1

Mass N3- ion = 14 g/mol. So,

4.2 g X (1 mol/14 g) = 0.3 mol N3-

Number of N3- ions = 0.3 mol X 6.02 X 10^23 ions/mol = 1.8 X 10^23 ions

Each N3- ion has 8 valence electrons, so total number of valence electrons = 1.8 X 10^23 X 8 = 1.4 X 10^24 valence electrons.

Answer 2

Answer: $14.45\times 10^{23}$ electrons.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}=\frac{4.2g}{14g/mol}=0.3moles$

Electronic configuration of nitrogen:

$[N]:7:1s^22s^22p^3$

Valence electrons of nitrogen = 5

$[N^{3-}]:10:1s^22s^22p^6$

Valence electrons of $N^{3-}$ = 8

1 mole of $N^{3-}$ contains =$8\times 6.023\times 10^{23}=48.18\times 10^{23}$ electrons

0.3 moles of $N^{3-}$ contains =$\frac{48.18\times 10^{23}}{1}\times 0.3=14.45\times 10^{23}$ electrons

Thus total number of valence electrons in 4.2g of $N^{3-}$ ion is $14.45\times 10^{23}$ electrons.