Why cl2o is called dichlorine monoxide while f2o is called oxygen difluoride?

Answer 1

Fluorine is more electronegative than oxygen, so it's named as the anion.

Chlorine is less electronegative than oxygen, so it's named as the cation.

Answer 2

The naming of covalent compounds follows a convention where the first element is named first, followed by the second element with an "-ide" suffix. In the case of Cl2O, it is named dichlorine monoxide because there are two chlorine atoms and one oxygen atom. Whereas F2O is named oxygen difluoride because there are two fluorine atoms and one oxygen atom.