[lucileburt]

 How to write chemical formulas in chemistry?
okay, i have no idea how to write (for example) sodium phosphate in its chemical formula. I know its Na3PO4, but how do i work this out?
has it got to do with the group that it's in - so the no. of ions in its outer shell?
and are there any ways to work it out easily? thanks you very much and of course 10 points for best answer thanks xx

[barbecue123]

How to write chemical formulas in chemistry?
okay, i have no idea how to write (for example) sodium phosphate in its chemical formula. I know its Na3PO4, but how do i work this out?
has it got to do with the group that it's in - so the no. of ions in its outer shell?
and are there any ways to work it out easily? thanks you very much and of course 10 points for best answer thanks xx

Exactly, you should take a look at the position of the element in the periodic table, at which gruop it belongs to. In the case of sodium phosphate you deal with a metal and an halogen compound, so it is an ionic bond. The Na is in the 1st group, so it has one positive charge in its ion form. the phosphate group case is more complicated, because this guy can have one, two or three negative charges. If you consider the fully deprotonated phosphate anion you should have three sodium cation (1 positive charge each) that come close (ionic bond) to a phosphate anion (3 negative charges): Na₃PO₄
I think in this case it's better "trisodium phosphate" than "sodium phosphate" (which is more generic)

[Arkcon]

Greetings, lucileburt:, I'd like to welcome you and all the new students to the Chemical Forums.  But I'd like to as you to trouble yourself to read our Forum Rules{click}. You already accepted them when you signed up for our forum, and they apply to you, whether you agree with them or not, or even if you're unaware of them. 

We want to see your work, and then, we want to give you hints, so that you learn for yourself.   Let's get started.

How to write chemical formulas in chemistry?
okay, i have no idea how to write (for example) sodium phosphate in its chemical formula. I know its Na3PO4, but how do i work this out?

OK, that's correct.  But what does it mean?  You start with 'Na'.  What's that?  Where's it from?  Its not from two-thirds of a 'banana', as has come up on our forums before.

has it got to do with the group that it's in

Oh good.  "Group that its in." We can start working with this.  What group, and where from?

- so the no. of ions in its outer shell?

OK.  That doesn't make sense as written.  Can you improve on this?

and are there any ways to work it out easily? thanks you very much and of course 10 points for best answer thanks xx