What percentage of the solar nebula's total mass was composed of primordial hydrogen ($ ext{H}$) and helium ($ ext{He}$)?

Answer

About 99.9 percent

Hydrogen and helium were the most abundant components, making up nearly all (about 99.9 percent) of the total mass available in the nebula due to their origin as the lightest products of the Big Bang.

What percentage of the solar nebula's total mass was composed of primordial hydrogen ($	ext{H}$) and helium ($	ext{He}$)?
Spaceastronomycompositionsolar systemformationcomponentssolar nebulaPlanetary Formation