The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic ...

A chemical element is one of those squares on the periodic table that adorns many a classroom wall. Sure. But what is an element really? It is a more subtle question that you might realise.

The same chemical symbols are used all over ... The atoms of other elements, however, like hydrogen, join with another hydrogen atom as a pair, making a molecule. So, all compounds are molecules ...