Mercury
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. Mercury is unusual because while most of these heavy atoms are solid at room temperature, the way you think of metal as a solid chunk of something, mercury is instead a liquid at room temperature. This is because mercury's outside electrons don't hold on to other mercury atoms very tightly or very well.
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.
Balls of mercury
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
To find out more about atoms, check out these books from Amazon.com or from your library:
