The relationship between the volume and mass of an element is

sonic say: Mass, volume and density are three of an object's most basic properties. Mass is how heavy something is, volume tells you how big it is, and density is mass divided by volume. Although mass and volume are properties you deal with every day, the idea of density is a little less obvious and takes careful thought

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.