# What is the bond polarity of CH4?

May 8, 2018

The dipole moment of a $\text{C-H}$ bond is probably 0.34 D.

#### Explanation:

We often say that a $\text{C-H}$ bond is nonpolar because the electronegativities of $\text{C}$ and $\text{H}$ are so close to each other.

However, the values are $\text{C = 2.55}$ and $\text{H = 2.20}$.

The difference corresponds to 3% ionic character, so a $\text{C-H}$ bond should have a small dipole moment.

From experimental IR intensities of methane, we can infer that µ_text(C-H) = "0.34 D", directed stackrelcolor(blue)(δ⁻)("C")"-"stackrelcolor(blue)(δ⁺)("H").

Theoretical calculations give varying results, but most experimental values are between 0.3 D and 0.4 D.