Why is the formula for magnesium oxide Mg3O2?

Answer 1

Nitrogen is in group 5A of the Periodic Table and needs 3e to complete the octet rule, Mg is in group 2A of the periodic table and can only give out 2e to complete the octet rule, hence the formula Mg3N2

Answer 2

This may be a little windy, but follow along, you might find this useful for later!!!

Nitrogen is in group 5A. The noble gases are in group 8A. In order for any atom to take on an ion configuration, it must mimic the electron configuration of the *NEAREST* noble gas. Nitrogen has an electron configuration of 1s2 2s2 2p3. If we add the electrons (2 + 2 + 3) we should get the number of protons in the atom (7). Nitrogen has 7 protons! We also get the number of valence electrons (2s2 2p3) which is 2+3 or 5. Did you notice that the number of valence electrons is equal to the group number? Pay attention to that, it'll save you time down the road!

In this case, the closest noble gas is Neon. Neon's electron configuration is 1s2 2s2 2p6. If we add it's valence electrons (2 + 6), we get 8, which is also it's group number. In order to match the valence electron configuration of Neon, we'd have to add 3 electrons to Nitrogen. This would mean our Nitrogen ion would now have 10 electrons. Since electrons have a negative charge, this atom would now a negative charge of 3. We would express this as N3-. We call this ion Nitride.

To put this into perspective, let's look at Beryllium. It's got an electron configuration of 1s2 2s2. This means that it has 2 valence electrons. It's also in Group 2A. In order for it to match the nearest noble gas (which is Helium), it must lose 2 electrons. Remember, it has to do this so that it ends up with the same ELECTRON CONFIGURATION as Helium. Helium's electron configuration is 1s2. Beryllium's electron configuration is 1s2 2s2. In order for Beryllium's ion electron configuration to match the electron configuration of Helium, it must lose it's 2 valence electrons (2s2). This ion now has the same amount of protons (4) but now only has 2 electrons. Because protons have a positive charge, the ion now has a positive charge of 2, so this becomes Be2+ (Beryllide).

Answer 3

Each molecule of magnesium oxide comprises three atoms of magnesium and two of oxygen.