Another Question! How do you know when to add or not to add a prefix when naming a compound?

please be specific as possible and give examples if you can. i have no idea when or when not to add a prefix or where to add it

Another Question! How do you know when to add or not to add a prefix when naming a compound?
When the compound involves two non-metals, you use prefixes such as monoxide and pentafluoride. In the compound N3O4 it is trinitrogen tetraoxide. But in compounds like NO4 you don't have to add "mono" to the nitrogen.
Reply:prefix when there is a covalent bond. ionic bond = no prefixs