Q. 6.155 - An Introduction to General, Organic, and Biological Chemistry

Question

Predict the shape of each of the following molecules: $(6.8)$

a. $N{H}_{2}Cl (N is the central atom)$

b. $Te{O}_2$

Step-by-Step Solution

Answer

a. The shape of $N{H}_{2}Cl$ is  trigonal pyramidal.

b. The shape of $Te{O}_2$ is Bent$\left(120°\right)$.

Part (a) step 1: Given Information

We need to find the shape of $N{H}_{2}Cl$.

Part (a) step 2: Simplify

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. 

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

the total valence electrons is $14$.

the central atom is $N$.

In order to complete the octet of the $N and Cl$atoms, there should be a single bond between the $N and Cl$ atoms and single bonds in $N and H$atoms.

Therefore, the Lewis structure of the molecule should be:

Based on VSEPR theory:

Geometry	Bonded	Lone  Pairs
Linear	$2$	$0$
Trigonal Planner	$3$	$0$
Bent $\left(120°\right)$	$2$	$1$
Tetrahedral	$4$	$0$
Trigonal Pyramidal	$3$	$1$
Bent $\left(109°\right)$	$2$	$2$

The molecule that its central atom $N$ has $3$ bonded atoms and $1$lone pair. So, the corresponding shape according to the VSEPR theory is trigonal pyramidal.

Part (b) step 1: Given Information

We need to find the shape of $Te{O}_2$.

Part (b) step 2: Simplify

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

$Te$is in group $6A$, it means it has $6$ valence.

$O$ is in group $6A$, it means it has $6$ valence.

The total number of valence electrons. 

$$\begin{gathered} total VE=6+2\times 6 \\ =6+12 \\ =18 \end{gathered}$$

the total valence electrons is $18$.

the central atom is $Te$ because there is only one of it in the molecule.

In order to complete the octet of the $O$, there should be a double bond between the $Te=O$ bond. So, the lewis structure of the molecule should be:

The molecule, the central atom $Te$has $2$ bonded atom and $1$ lone pair. So, the corresponding shape according to the VSERP theory is Bent $(120°)$.