Use this poster, fact sheet and peer-assessment activity to help your post-16 students understand orbitals and shells

Three diagram showing how electron shells and orbits relate to the periodic table

Source: © Dan Bright

A teaching guide to boost post-16 students’ understanding on orbitals and shells

We describe most chemical changes in terms of a rearrangement of electrons. It’s therefore crucial to have an accurate understanding of the arrangement of electrons (the electron configuration) in atoms and ions. Electron configurations give us insight into the bonds that atoms are likely to form and the relative stability of ions.

Shells are the allowed energy levels of electrons. The first shell has the lowest energy and the energies increase as the electrons get further away from the positively charged nucleus.

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Infographic poster and fact sheet, student worksheet and teacher notes for peer-assessment activity. Display the poster in your classroom or on a projector. Alternatively print it and use as a handout.

Use the accompanying activity to check your post-16 learners’ understanding by asking them to correct and improve incorrect electron configurations.



All shells are subdivided into different energy levels called subshells, with the exception of the first shell which is not subdivided. The second shell is divided into two subshells: s and p. The third shell is divided into three subshells: s, p and d.

A diagram showing how electron shells of an atom increase in energy level as they go out

Source: © Dan Bright


Each subshell contains different shaped orbitals – regions in space where we are likely to find electrons. Each orbital can contain just two electrons, which must have opposite spin from each other.

A diagram showing the different shapes of electron shells - 2s is spherical, 2pz, 2px and 2py are dumbell shaped on different axis

Source: © Dan Bright

More resources

Sodium (Na) is in the s-block of the periodic table, which is two elements wide. The p-block contains elements with their highest energy electrons in the p subshell and is six elements wide.

An outline of the periodic table showing how the different blocks relate to the different electron shells

Source: © Dan Bright

Did you know …?

The labels s, p, d and f come from the appearance of lines in line spectra. They stand for sharp, principal, diffuse and fundamental.

 All illustrations © Dan Bright