Answer: C. 1
Explanation:
If you look at a periodic table, group 13 includes boron, aluminium, gallium, and other elements. For these elements, they all have a filled s-orbital, (because if we look at boron (a group 13 or 3A element), it is right ahead of lithium and beryllium, both s-orbital elements) which means they get two extra electrons before the p-orbital. Since boron is only one space into the p-orbital, it gets 1 electron. 1 from the p-orbital plus 2 from the s-orbital = 3 electrons in their outer-most shell. Number one also has 3 electrons so that is your answer.
