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a diagram of a mercury atom showing a whole lot of electrons circling a big nucleus

Diagram of a mercury atom. Thanks to Open Door for this image

Along with gold, lead, and uranium, mercury is one of the heavier kinds of atoms. Every atom of mercury has 80 protons and 121 neutrons in its nucleus.

Like those atoms, all mercury atoms are made inside older stars that have become supernovas. Most of these heavy atoms are solid at room temperature, the way you think of metal as a solid chunk of something. But mercury is unusual: it is a liquid at room temperature. That’s because mercury’s outside electrons don’t hold on to other mercury atoms very tightly or very well.

balls of mercury: silver globes on a wooden deck

Balls of mercury

On Earth, mercury is pretty rare. It usually combines with sulphur molecules to make a rock called cinnabar. We get mercury by crushing the cinnabar and roasting it in ovens. Because mercury is liquid at room temperature, but expands slowly as it is heated, people use it inside thermometers to measure heat.

Learn by doing – Mercury Thermometers

Bibliography and further reading about mercury:

The planet Mercury
Chemistry home