Allotrope
From Conservapedia
If a pure element can form several physically and chemically different substances, it can form allotropes. For example, O2 and O3 are allotropes of oxygen.
The most famous element that can form allotropes is carbon, which can form four. The following elements can also form allotropes: phosphorus (3), oxygen (3), sulphur (4), and plutonium (7).
