Some Basic Concepts of Chemistry - Result Question 26
####25. If $N_A$ is Avogadro’s number then number of valence electrons in $4.2 g$ of nitride ions $(N^{3-})$ is
(a) $2.4 N_A$
(b) $4.2 N_A$
(c) $1.6 N_A$
(d) $3.2 N_A$
[1994]
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Solution:
- (a) No of moles of nitride ion
$=\frac{4.2}{14}=0.3 mol=0.3 \times N_A$ nitride ions.
Valence electrons $=8 \times 0.3 N_A=2.4 N_A$
Nitride ion has seven protons in the nucleus and ten electrons surrounding the nucleus. Therefore total no. of electrons is 10 . Number of valence electrons is $(5+3)=8$.
