Electrons and atoms are said to be quantized . Electron levels Electrons tend to group themselves into orbits and sub-orbits. Orbit 1, the K orbit shell, is filled by the s sub-orbit. Orbit 2, the L orbit shell, is filled by the s and p sub-orbits. Orbit 3, the M orbit shell, is filled by the s, p and d sub-orbits.
Electrons tend towards the lowest energy level.
Review periodic table. Elements with full shells tend to be inert. Elements with 1 valence electron tend to be highly reactive. Relations on the periodic table. For the A groups, or columns, the number next to A tells you the number of valence electrons.