How Are Atoms & Elements Related?
Atomic number defines an element, with various atomic weights often existing under the domain of a single element. Phase (solid, liquid, gas) is an emergent property caused by atomic/molecular thermodynamics. Radioactivity allows for elements to change due to nuclear decay altering atomic number. While element properties predicted from their atoms are substantial, they are not all-encompassing. Atomic Number Atomic number is the number of protons in the nucleus; this number defines element identity. Atomic Weight Atomic weight (but not number) can vary within a single element. For example, Carbon-12 and Carbon-13 differ by an extra neutron in C-13. Both isotopes have the same chemistry, but C-13 is slightly heavier. Element Phase Atomic energetics and mass under a given temperature/pressure condition dictate in what state (solid, liquid, gas) an element exists at that temperature and pressure. For instance, Radon is a heavy atom (atomic weight 222), but exists as a gas at room temperat
