The formula for terbium phosphate is TbPO4. The formula for terbium sulfate is... How do I figure out how many of each element to use?

Question

aaronq · Answer

TbPO4 is made up the terbium ion and the phosphate ion. 

the phosphate ion is a common polyatomic ion with a charge of -3, so in order to balance the charges (and have an neutral compound) the terbium ion has to be +3.

What charge is the polyatomic sulfate ion?

Once you know that (you can look it up in your book or online) you can figure out how many terbium +3 ions you need to balance the charges (make the charge zero).

anonymous · Answer

Sulfate, SO4 has a -2 charge, so Tb would have to be 2+

anonymous · Answer

No, to balance it you would have to switch the charges, Soo Tb2 (SO4)3

aaronq · Answer

yep! that's right.  btw, the charge on terbium would not change from 3+.

anonymous · Answer

Oh okay! Thanks!