Electrons are arranged in shells around the nucleus of the atom. Each shell is shown as a circle drawn around the chemical symbol for the atom. The way in which the electrons are arranged in an atom is called its electronic configuration.
Different shells contains different numbers of electrons, For the first 20 elements:
- the first shell can contain up to two electrons
- the second and third, etc, can hold up to eight electrons
Electronic configurations can be worked out using atomic numbers. For example, the atomic number of sodium is 11. This means that there are 11 protons and also…