Electron Orbital

Key Stage 3

Electron shells are the places around a nucleus where an electron can orbit the nucleus.


A diagram of a Sodium atom shown the electron shells.

The number of electron shells is shown by the period on the Periodic Table.

The number of electrons in the outer shell determines the chemical properties of the element.


A diagram of the first 20 elements in the Periodic Table showing the electron shells.

A diagram showing the three electron shells of a Sodium atom.

Electron orbitals, also known as an electron shells, are the locations where electrons orbit the nucleus of atoms.

Each electron orbital only holds a certain number of electrons.

The first orbital can only hold a maximum of 2 electrons.

The second orbital can hold a maximum of 8 electrons.

The third orbital holds a maximum of 8 electrons.

You do not need to know the numbers beyond this at Key Stage 4.

These orbitals and the number of electrons in an atom determine the chemistry of an element.

The number of electron orbitals determines the Period on the Periodic Table.

The number of electrons in the last orbital (Outer Shell) determines the Group on the Periodic Table.


A diagram showing the electron shells and electrons in the first 20 elements on the Periodic Table. NB Group 0 used to be called Group 8 but this caused confusion because most elements in Group 8 have 8 electrons in their Outer Shell but Helium only has 2, so it was renamed Group 0.

Atoms in the same group have similar chemical properties because they all have the same number of electrons in their Outer Shell.