Allotropy and allotrope are terms related to the different forms that an element can take. However, they refer to slightly different concepts.
Allotropy is the ability of an element to exist in two or more different forms in the same physical state. These different forms can have distinct physical and chemical properties. For example, carbon is an element that exhibits allotropy; it can exist as diamond, graphite, and fullerenes, each with unique characteristics.
On the other hand, an allotrope is one of these distinct forms of an element. Using our earlier example, diamond and graphite are both allotropes of carbon. Each allotrope varies in its arrangement of atoms and the bonds between them, which gives rise to the differences in their properties.
In summary, allotropy refers to the phenomenon of an element existing in multiple forms, while an allotrope specifically denotes one of those forms. Understanding this distinction helps clarify discussions in chemistry related to the properties and behaviors of elements.