# What class of elements are providing the many electrons needed to make the H- ion?

Continuous absorption by the H- ion reaches its maximum in the cool atmospheric layers of G stars. At these temperatures, most of the hydrogen atoms are neutral; but what class of elements is providing the many electrons needed to make the H- ion?

• Any prior research? You don't want people to quote papers that you've already read. – James K Apr 15 '20 at 5:17

You don't need many free electrons. The fraction of H$$^{-}$$/H is very small, something like $$10^{-7}$$ in the solar photosphere. And indeed the number densities of sodium and potassium to hydrogen are of that order.