What do the atomic numbers found on the periodic table of the elements indicate?

 The atomic number of an element suggests the number of protons in the nucleus of that element. You know the number of protons in an atom is equal to the number of electrons in that atom. So we can, with this number, predict the electronic configuration of the atom.

Let's take the example of sodium, which has an atomic number of 11.

With this information, we know that in sodium, the number of electrons and protons are both 11. The distribution of electrons will thus be in the three innermost shells (K, L M) in a 2-8-1 configuration. This configuration gives us information on the position of sodium in the periodic table as period 3 and group 1. Period 3 because the electronic configuration is possible with three shells (K, L and M) and group 1 because the outermost shell has 1 electron. This is also called a valence electron, it indicates the valency of an atom.

Question asked by: Anunandha K M, VIII C