Beryllium-7
= Beryllium-7
{title2=$^7\mathrm{Be}$}
Beryllium-7 contains four <protons> and three <neutrons>. It forms in reactions including $^3\mathrm{He}+{}^4\mathrm{He}\to{}^7\mathrm{Be}+\gamma$ and becomes <lithium-7> through <electron capture>. In the early universe its ionization state affects when capture occurs, so the final primordial lithium inventory includes the earlier beryllium inventory rather than just lithium present when nuclear burning ends.