[alexanda]

Is that mean when the charge is opposite, they are matters and antimatters?

[mjc123]

No. The antimatter counterpart to the proton (H⁺) is the antiproton, which is like a proton but with a negative charge. H^- is not an antiproton but a hydride ion, a proton with two electrons (isoelectronic with the He atom) with an overall charge of -1. If you put H⁺ and H^- together, you don't get annihilation, you get an H₂ molecule.

[alexanda]

Ok thx a lot!