# What are the protons, neutrons, and electrons for a sulfur(2-) anion with a mass number of 33?

Dec 11, 2016

Well, number of protons is easy. It's $\text{sulfur, Z = 16} ,$ so there are 16 $\text{nucular protons}$.

#### Explanation:

If there are 16 positively charged particles, there must be 16 negatively charged particles in the $\text{neutral}$ element. We have ${S}^{2 -}$, and thus there must be $18$ electrons associated with the ion.

And neutrons for ""^33S? Well, the electrons are along for the ride, and have zero rest mass. The mass of an atom, to a first approximation, is the number of massive, nuclear particles, i.e. the number of $\text{protons and neutrons}$. We have $16$ nuclear protons, so there MUST BE $17$ $\text{neutrons}$, i.e.

${33}_{\text{the mass number")=16_("protons")+17_("neutrons}}$.

Are you happy with this? If you think it is simple, it should be, but many students are unconvinced by this apparent simplcity.

From where did I get these numbers?