State which type of ionising radiation has a negative charge.

The equation shows how an isotope of radium decays to become an isotope of radon.

${}_{88}{}^{223}\mathrm{Ra}\to {}_{86}{}^{219}\mathrm{Rn}+{}_2{}^4\mathrm{H}+\mathrm{energy}$

Here, we can check that the equation is balanced by counting the number of nucleons before and after the decay, and the number of protons before and after.

For the nucleons, we have $223=219+4$.

Show that the number of protons is the same before and after the decay.