First of all, the one in the left is the most electronegative element. The first letter of an element must be in uppercase letter
So, in ionic compound, e.g., Metal + Nonmetal compound (Sorry for the comment, it is wrong), you name it with the suffix -ide with the element in the right hand side. Example: Sodium Chloride
Another is the covalent compound, e.g., Nonmetal + Nonmetal compound. you name it with numerical Ancient Greek word before the element name and add the suffix -ide in the right hand side element. Example: Dihydrogen Monoxide
