Formulas and names

[pjluva10]

So I missed the day we went over this in class and am a bit lost.  I need to learn how to find chemical names and formulas.  Examples of the ones that I am struggling with are

Magnesium, phosphorus and oxygen
Potassium, silicon and oxygen
Arsenic, Gallium and oxygen. 

I'm not looking for the awnsers since I need to learn how to do this.  Any help is appreciated.

[kingchemist]

Compounds which contain more than 2 elements where one is oxygen either end in the letters - ITE or - ATE (where the ending indicates the presence of Oxygen)

eg copper sulphate = CuSO4
sodium sulfite = Na2SO3

Metal comes first in the name so magnesium phosphate, potassium silicate

The last one is less obvious but Ga is a metal so gallium arsenate would be the answer

Have a look at the chemistry tutorials I wrote on formula and found under 'atomic theory' in the tutorial section.