# What is the charge on a "surfactant"?

Surfactants are usually the alkali metal salt of a long chain fatty acid. So the answer is $\text{anionic}$.
To a first approximation a surfactant, a detergent, is the salt of a carboxylic, or sulfonic acid, with a long alkyl chain attached. The counterion is usually a simple metal cation, i.e. $N {a}^{+}$. The alkyl chain does the business of combining with grease and oil, and entrapping it so that your washing up gets clean. Think about this the next time you do the dishes!