For elements in the first three periods of the periodic table (hydrogen - argon), the orbitals can simply be filled up by increasing energy energy level. A difficulty arises when we come to potassium.

There’s another "ah" moment at A-level when you introduce orbitals, and suddenly students understand why there’s a p-block or an s-block. Imagine being at the start of this journey, where you've got ...

Bismuth is in Group 15 of the periodic table. The s, d and f orbitals are all full, but the p orbitals contain three out of a ...