The zigzag, staircase, line in the diagram of the periodic table above separates the metals, on the left, from non-metals, on the right. Hydrogen is a non-metal, but it is often put in the middle.

In this series, podcast presenters Dr Sunayana Bhargava and Tulela Pea guide you through everything you need to know about atomic structure and the periodic table to ace your GCSE science exam.