About how many "times" bigger is 9 x 107 than 1.5 x 107?
9
1
2.
6

A magnesium atom is a neutral atom where the number of protons and electrons are the same. A magnesium ion has a positve 2 charge since it will lose two of its electrons when it undergoes ionic bonding. Since it's the same element it will still have the same amount of 12 protons. For isotopes of magnesium, they will have differing amounts of neutrons and thus a difference in the mass number since neutrons have a mass of about 1