Instant Chemistry help!

So I have a test tommorow in chemistry and theres one major thing I do not understand. When naming chemical formulas, how do you know when to add a "di" infront of the element?
For example: dichloride. <------

You add a di when there is 2 of the element in the compound, such as in water. The chemical equation for water is H20. The official name is dihydrogen monoxide. (Mono is one, and there is one of oxygen, however you never put mono if it is at the beginning.)

Greek prefixes like "mono, di, tri" etc. are used when the compound you are trying to name is made of two NONMETALS, like CO (carbon monoxide) and CO2 (carbon dioxide). Nonmetals are located on the right side of the period chart. SO2 would be sulfur dioxide (the "mono" is never used with the first element); SO3 would be sulfur trioxide. N2O2 would be dinitrogen dioxide etc.

You only use di in front of an element when you have a covalent molecule, when you have ionic bonds, there is no need to use di because you can tell the charges of each element by their position on the periodic table.
So, only use di when you have all nonmetals.

Di means 2 so, if its co2 its carbon dioxide meaning 2 oxygen atoms, what grade r u in

They may be right Snowflake, but don't let those jerks get you down. I'm sure you would have figured it out.