<p>Easily ionised ones like sodium and potassium. Not much from lithium because that is rare.</p>

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

CC BY-SA 4.0
2020-04-15T07:30:25.407Z
2020-04-15T07:30:25.407Z
ProfRob
<p>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?</p>

CC BY-SA 4.0
2020-04-15T05:17:11.023Z
Any prior research? You don't want people to quote papers that you've already read.
James K
<astrophysics><opacity><photosphere>
What class of elements are providing the many electrons needed to make the H- ion?
Boris
# What class of elements are providing the many electrons needed to make the H- ion?

(Asked by: username_0 on 2020-04-14)

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?

**Tags:** astrophysics, opacity, photosphere

> **Comments:**
> **username_1**: Any prior research? You don't want people to quote papers that you've already read.  

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## 1 answers

### Answer by username_2 on 2020-04-15. Score: 5 | Accepted answer

Easily ionised ones like sodium and potassium. Not much from lithium because that is rare.

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.


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