If I have 13 protons and 12 electrons what is my charge?

The charge would be +1

Explanation:

Protons have a positive charge while electrons have a negative charge. Therefore, it's simple subtraction. In every case, subtract the number of electrons from the number of protons.

13 - 12 = 1

Therefore the charge is +1

Here's one more example:

If the element chromium (Cr) has 24 protons and 28 electrons, what is its charge? Remember that protons have a positive charge and electrons have a negative charge.

24 - 28 = -4

Charge = -4

It would be written as followed when associating charge with a specific element:

If an element has a neutral charge, that means the number of protons and neutrons are the same. If you look at the periodic table of elements, all of the elements listed have a neutral charge. The 0 isn't showed in the corner because it isn't necessary.

Bonus Information:

This isn't related to your question, but I've come across confusions when it comes to particles. Remember that protons (+) and electrons (-) are the only particles that have a charge, therefore, as it says in it's name, neutrons are neutral or have no charge. Neutrons do not contribute to charge, but they do contribute to the mass of an atom. So the number of protons added to the number of neutrons equate to the mass of an atom. Electrons have mass, but it's so miniscule and insignificant that it doesn't even contribute to the overall mass of the atom, so don't count those.

Remember:

C = p - e

M = p + n

C = atomic charge, M = atomic mass, p =protons, n = neutrons, e = electrons

I hope this helps!