Sodium lauryl sulfate (SLS) is an anionic surfactant, meaning it has a negatively charged head group. The valence of SLS is -1.

Here's why:

* Sodium (Na) has a +1 charge.

* Lauryl sulfate (C12H25SO4) has a -1 charge.

Therefore, the overall charge of SLS is +1 - 1 = 0. This means that SLS is a neutral molecule overall, but it carries a negative charge on the sulfate group, making it anionic.