2. What is the difference between mass and weight

Mass is the amount of matter in a material, while weight is a measure of how the force of gravity acts upon that mass.

Explanation:

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.