Question

How many protons and electrons are present in the mg2+ ion? 1. 14 protons, 14 electrons 2. 12 protons, 10 electrons 3. 12 protons, 12 electrons 4. 14 protons, 12 electrons 5. 10 protons, 12 electrons 6. 10 protons, 14 electrons 7. 14 protons, 10 electrons 8. 12 protons, 14 electrons 9. 10 protons, 10 electron?

Answer 1

There are 12 protons and 10 electrons in a Mg2+ ion, the normal amount of neutrons is 12.

Explanation:

Magnesium is an element with atomic number 12. This means that every magnesium atom will have 12 protons. 

In a magnesium atom, there are 12 electrons, to make the atom have a neutral charge. When an ion is formed, the magnesium atom loses electrons. The 2+charge shows that the magnesium ion has two more protons than electrons. The proton number for magnesium does not change, so Mg2+ must have two less electrons, i.e. 10 electrons.

The number of neutrons varies among different isotopes of magnesium. An isotope of an element means it just has different amounts of neutrons.

The most common isotope of magnesium is 24Mg. This 24 indicates the total number of protons and neutrons. Magnesium has 12 protons, so must have 

24−12=12 neutrons

Other isotopes of magnesium have different numbers of neutrons, i.e. 25Mg has 13neutrons, 26Mg has 14 neutrons. 24Mg is most likely being referred to in the question, though.