When elements are listed in order by the masses of their atoms, the same sequence of properties appears over and over again in the list.
Learning Goal 7a
Atoms often join with one another in various combinations in distinct molecules or in repeating three-dimensional crystal patterns.
Learning Goal 9a
The rate of reactions among atoms and molecules depends on how often they encounter one another, which is affected by the concentration, pressure, and temperature of the reacting materials.
Learning Goal 10
The physical properties of compounds reflect the nature of the interactions among its molecules. These interactions are determined by the structure of the molecule, including the constituent atoms and the distances and angles between them.