Our answer: Al3+
Let me tell you why. Since this has 13 protons, we already know that when an atom is positive (ionic), means that it lost electrons. Since they have a 3+, we know that it lost 3 electrons.
Protons = 13
Electrons usually equal the amount of protons, but it lost three in this case, so we subtract 3 from 13.
13 - 3 = 10
Now, we know that it has 10 electrons.
