Electronic Configuration

Protons and neutrons can be found in the nucleus of an atom. However, electrons are arranged differently, as you can see from here:

The e-s represent electrons. The 1st shell of an atom, the shell closest to the nucleus, can only contain a maximum of 2 electrons. The 2nd, 3rd and 4th shell however, can contain up to a maximum of 8 electrons each.

The electronic configuration of an element is somewhat a representation of the diagram using numbers and dots.

For example, when an atom has 8 electrons, the electronic configuration will be 2.6 .
When an atom has 20 electrons, the electronic configuration will be 2.8.8.2 .

The image I inserted is knwon as an electronic structure.