​Once you are good with the prefixes, then you can write a formula or name a compound.



Writing the Formula:

1. Carbon Monoxide ---> 1 Carbon, 1 Oxygen ---> CO

2. Sulfur Hexafluoride ---> 1 Sulfur, 6 Flourides ---> SF6

3. Dihydrogen Monoxide ---> 2 Hydrogen, 1 Oxygens --->H20



Naming a Compound: Prefix + name of 1st element   Prefix + name of 2nd element (drop the last syllable and end in –ide)



1. N​2O​ ---> 2 Nitrogen ---> 1 Oxygen ---> ​Dinitrogen Monoxide​



2. PH​3 ---> 1 Phosphorus ---> 3 Hydrogen ---> Phosphorus Trihydride



3. Se3Cl6 – have 3 selenium ---> triselenium --->  have 6 chlorine

--->  hexachloride ---> Triselenium Hexachloride