Question

What is the chemical name for `"Na"_2"O"` ?

Answer 1

Sodium oxide.

Explanation:

The first thing to notice here is that this compound contains a metal, sodium, and a nonmetal, oxygen, so right from the start, you know that you're dealing with an ionic compound.

Now, sodium is located in group 1 of the Periodic Table, which means that an atom of sodium has `1` valence electron. In order to complete its octet, sodium will lose this valence electron and form the sodium cation, `"Na"^(+)`.

Oxygen, on the other hand, is located in group 16 of the Periodic Table, which means that an atom of oxygen has `6` valence electrons. In order to complete its octet, oxygen takes in `2` electrons and forms the oxide anion, `"O"^(2-)`.

In order to name this compound, use the name of the cation first and the name of the anion last.

You will have

`"Na"_ 2"O" -> 2color(blue)(["Na"]^(+)) + color(red)(["O"]^(2-)) -> color(blue)("sodium") quad color(red)("oxide")`

Notice that the sodium cation carries a `1+` charge and the oxide anion carries a `2-` charge, which is why you need `2` sodium cations to balance the overall negative charge coming from `1` oxide anion.