Classify each of the following molecules as polar or nonpolar:$\left(6.7,6.8,6.9\right)$

a. $N_2$

b.$N{H}_{2}Cl$

We need to classify whether the molecule $N_2$is polar or nonpolar.

A polar molecule is a molecule where there is a net electronegative difference within the molecule. There is a net electronegative difference when the polar bonds in the molecule are not symmetric.

If there is no net electronegative difference, then the molecule is nonpolar.

The electronegative of $N$is $3.0$. So both atom in the molecule are $N$atoms, the electronegativity difference between the atom is $0.0$making the bond nonpolar covalent.

We need to classify whether the molecule $N{H}_{2}Cl$is polar or nonpolar.

Here, identify the total number of valence electrons in each molecule.

$H$is in group $1A$, it means it has $1$valence.

$N$is in group $5A$, it means it has $5$valence.

$Cl$is in group $7A$, it means it has $7$valence.

The total number of valence electrons.

$$\begin{gathered} totalVE=2\times 1+5+7 \\ =2+12 \\ =14 \end{gathered}$$

the total valence electrons is $14$.

the central atom is $N$In order to complete the octet of the $NandCl$

atoms, there should be a single bond between the $NandCl$atoms and single bonds in$NandH$atoms.

Therefore, the Lewis structure of the molecule should be:

According to the VSEPR theory is trigonal pyramidal, and the molecule is polar. The uneven distribution of electron density.