# What is the bond angle in cumulene (C4H4), of the C=C=C bond and the H-C-H bonds?

Dec 23, 2015

The $\text{C=C=C}$ bond angle is 180°, and the $\text{H-C-H}$ bond angle is 120 °.

#### Explanation:

The structure of cumulene is

The $\boldsymbol{\text{C=C=C}}$ bond angles

The internal carbon atoms are each directly bonded to two other carbon atoms, so they are each ${\text{AX}}_{2}$ systems.

According to VSEPR theory, the bond angle in an ${\text{AX}}_{2}$ system is 180 °

The $\boldsymbol{\text{H-C-H}}$ bond angles

Each carbon atom is directly bonded to three other carbon atoms ($\text{C, H}$, and $\text{H}$), so they are each ${\text{AX}}_{3}$ systems.

According to VSEPR theory, the bond angle in an ${\text{AX}}_{3}$ system is 120 °