Can someone help with naming chemical formulas?

i have to identify the ionic compound, potassium phosphate and it says the answer is K3PO4. Where does the three come from?

Can someone help with naming chemical formulas?
well you have to see what the ions look like when they break up. You have K(+) and PO4(-3). When combined you need 3 K(+) to balance out the one PO4(-3). Its to balance the ionic charge.
Reply:The phosphate ion, PO4, has a valence (electrical charge) of -3. That means it needs to share three electrons with a positively charged ion in order to be happy. Each potassium ion, K, has a charge of +1. It will therefore take three potassium ionically bound to the phosphate to form one happy little neutral molecule.