What is the primary reason we divide the ingredients of the solar nebula into four categories (hydrogen/helium gas; hydrogen compound; rock; metal)?

Ibelieve its because the stove is a cleaner burning fuel

Hello thereone of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description? answer: atomic mass  was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

Answer(d) unstable compounds that convert to acetals in the presence of alcohol and an acid; (b) semiacetals produced by alcohol subtraction from ketone;