Note. The maximum number of electrons that any quantum level
can accommodate is seen to be given by the formula 2n2 where n is
the number of the quantum level, for example n — 3: the maximum
number of electrons is therefore 18.
An orbital is characterised by having a single energy level able to
accommodate two electrons. The three p orbitals and five d orbitals
are given symbols to differentiate them, for example px, pr p..
representing three orbitals at right angles each capable of containing
two electrons.