Which is a characteristic of all ions?

a. They are made of one type of atom.

b. They have one overall charge.

c. They are made of two or more types of atoms.

d. They have two or more overall charges.

I believe the answer is:

B. They have one overall charge.

The answer is B - they have one overall charge. Atoms are neutral, meaning they contain the same number of protons as electrons. When you remove an electron from this atom you get a positively charged ion that has a net charge of + 1. By adding an electron, however, you get a negative charge on the ion.