Question

When is the only time you don't use prefixes when naming covalent compounds?
If it's a diatomic molecule like H2
If it's the first element in the compound and there is only one present
If it's a diatomic molecule or if it's the first element in the compound and there is only one present
You always use prefixes in all covalent compounds

Answer 1

answer: If it's the first element in the compound and there is only one present.  for example consider CO it is named as carbon monoxide not as mono carbon monoxide. when the first element is single there will not be any prefix.  consider N2S5 it is named as dinitrogen pentasulfide as the first element is not mono it is named with prefix.

Answer 2

If it's a diatomic molecule or if it's the first element in the compound and there is only one present