91Ó°ÊÓ

In covalent molecules or molecular ions, the bond angles between the bonds around a central atom depend on its geometry, which depends on the total number of -bond pairs and lone pairs.

• If the count of valence shell electron pairs is 2, the geometry will be linear with a bond angle of $180°$.
• If the count of valence shell electron pairs is 3, the geometry will be trigonal planar with a bond angle of$120°$ .
• If the count of valence shell electron pairs is 4, the geometry will be tetrahedral with a bond angle of$109°28\text{'}$ .

a. The count of valence shell electron pair is 2 for each carbon atom and has a linear geometry. So, the bond angle formed will have a value of$180°$.

Representation of bond angles of a

b. The count of valence shell electron pair is 3 for the central carbon and has a trigonal planar geometry. So, the bond angle formed will have a value of nearly $120°$.

Representation of bond angles of b

c. The count of valence shell electron pair is 4 for the central carbon atom and has a tetrahedral geometry. So, the bond angle formed will have a value of $109°28\text{'}$.

Representation of bond angles of c