The reactivity of an element is based on its . protons electrons 2. electrons are the most important electrons to an atom. Outer Inner 3. refers to how reactive a substance is with oxygen. Reduction Combustibility

Why does earth rotate? because earth is formed from cold gases collapsing due to gravity because the matter in the nebula that formed earth was spinning because earth forms more than 99% of the mass of the solar system because the hydrogen atoms inside the nebula fused to form helium