The 3 indicates the third electron shell. (Which has only 1 electron in it in this configuration)
Hope this helps! :)
Since nonmetals have five, six, or seven electrons in their valence shells, it takes less energy to gain the necessary electrons, and therefore form anions.
If you’re given molecular weight, you know that density is mass/volume. You need to convert the molecular weight to volume. If you know what molecule it is, use the gram formula mass to convert it into grams.
