Q. 6.71 - An Introduction to General, Organic, and Biological Chemistry

Question

Choose the shape $(1 to 6)$ that matches each of the following descriptions (a to c):

1. linear
2. bent $(109°)$
3. trigonal planar
4. bent $(120°)$
5. trigonal pyramidal
6. tetrahedral 

(a) A molecule with a central atom that has four electron groups and four bonded atoms.

(b) A molecule with a central atom that has four electron groups and three bonded atoms

(c) A molecule with a central atom that has three electron groups and three bonded atoms

Step-by-Step Solution

Answer

Shapes according to given description are:

(a) Tetrahedral ; Option $6$

(b) Triagonal Pyramidal; Option $5$

(c) Triagonal Planar; Option $3$

Part (a) Step 1: Given Information

We need to find shape of molecule according to description:

 A molecule with a central atom that has four electron groups and four bonded atoms. 

Part (a) Step 2: Explanation

A molecule with four electron groups on its core atom and four linked atoms has zero lone pairs. As a result, it's tetrahedral. Below is representation of tetrahedral shape. 

Part (b) Step 1: Given Information

We need to find shape of molecule according to description:

A molecule with a central atom that has four electron groups and three bonded atoms 

Part (b) Step 2: Explanation

A molecule with four electron groups on its core atom and three bonded atoms have one lone pair on its central atom forming bond angle of $109°$ has shape of triagonal pyramidal. A triagonal pyramidal shape is depicted below.

Part (c) Step 1: Given Information

We need to find shape of molecule according to description:

A molecule with a central atom that has three electron groups and three bonded atoms 

Part (c) Step 2: Explanation

A molecule three electron groups on central atom and three bonded atoms have zero lone pairs on its central atom forming bond angle of $120°$ form triagonal planar shape. Below is representation of triagonal planar shape.