In H2SO4 how to determine the charge of H2 and SO4?

The charge for hydrogen is 1+, and sulfate is 2-.

Sulfuric acid, ##H_"2"SO_"4"##, is an acid with a hydrogen atom and a sulfate atom.

What I personally do, is reverse the subscripts:

What's happening in the image is sodium's subscript changes into a superscript, transferring to the other atom, thus sulfur's charge is 2. We know sodium is a cation and sulfur is an anion, so the electrical charge is -. Therefore, the charge for sulfur is 2-. We do the same for sodium.

In ##H_"2"SO_"4"##, the compound is molecular, but hydrogen is a cation (in this case), so it is acting as a metal (but it's not).

We do the same as ##Na_"2"S##, the subscript for hydrogen is 2. So we turn it into a subscript and transfer it to the sulfate ion. It being an anion, it gets a negative charge, thus 2-. Doing the same to hydrogen, we get the subscript (which is 1), and turn it into a superscript. Then transferring it to hydrogen. Since hydrogen is acting as cation, it gets a positive charge.

The charge for hydrogen is 1+, and sulfate is 2-.

Hope this helps :)