i need help with giving charges and understand

Question

.Give the charge( SO3) 2-=

AsO43-=

.Au3PO4=_

Cr2O3

Answer 1

Some general rules (there are exceptions):

O has a charge of 2-

H has a charge of 1+

most others can be determined from the group number in the periodic table,e.g. Na=1+, Mg=2+, Al=3+

Cl=1-, S=2-, N=3-,etc.

SO₃^2- Since O is 2- and there or 3 of them, that = 6-. The S must be 4+ in order to have a net charge of 2-

AsO₄^3- There are 4 O with each being 2- so that's 8-. In order to have a net of 3-, the As must be 5+

Au₃PO₄ The polyatomic anion PO4 has a 3- charge, and since there are 3 Au atoms, each must be 1+

Cr₂O₃ Three O each at 2- so that's 6-. Thus, each Cr must be 3+ to balance the 6- leaving no net charge.