On the Periodic table, a period is a horizontal row of elements, while a group is a vertical column of elements. Elements in a group have similar properties. Elements in a period cover a specific range of atomic numbers regardless of properties. Periods begin with an easily-ionized, chemically active metal and end with difficult-to-ionize, chemically inert gas.
The similarities and periodicity in chemical properties result from the fact that each electron in an atom must be a little different from all the others. They differ in "size", via the principal quantum number n, in "shape" via the angular momentum quantum number l, in "orientation" via the axis-directed angular momentum quantum number m, and in inherent electron angular momentum (spin).
Periods[]
- "Period 0" (discredited)
- Period 1
- Period 2
- Period 3
- Period 4
- Period 5
- Period 6
- Period 7
- Period 8 (theorized)
- Period 9 (speculated on)
- Period 10 (speculated on)
- Period 11 (speculated on)
(05-12-20)