A red sun

I find it hard to choose when students ask me for my favourite element, but phosphorus ranks quite highly. Like carbon and sulfur, it displays a range of allotropes with interesting structures and properties to discuss. One of the most iconic phosphorus demonstrations involves igniting white phosphorus in a large round bottomed flask filled with oxygen to produce a magical glowing ‘sun’.

Many think the experiment can only be performed with white phosphorus, which is hard to acquire and difficult to handle safely. But this isn’t the case – exactly the same astonishing effect can be produced with red phosphorus.

This demonstration is ideal for use with lessons on periodicity. Lower school students may need to appreciate that the oxides of non-metals form acids and that these play a role in acid deposition. Older students are often required to know the properties of the period 3 elements and the reactions of their oxides with water.

With an accompanying video, Declan Fleming demonstrates how to make a glowing sun with red phosphorus, from preparation to presentation and classwork around this.