The term allotrope refers to one or more physical forms of a chemical element that occurs in the same physical state. Allotropes may show differences in chemical and physical properties. Swedish chemist Jons Jakob Berzelius proposed the concept of allotropy in 1841. The word “allotropy” comes from the Greek word allotropia, which means changeableness.
Properties of Allotropes
- Allotropes are various structural types of the same element and therefore can exhibit different physical and chemical properties.
- The allotropic forms change is caused by the same forces that influence other structures, namely light, pressure and temperature.
- Thus the stability of the different allotropes relies on specific conditions.
- Diamond and graphite (two allotropes of carbon) have different appearances, hardness values, melting points, boiling points, and reactivities.
- Some elements have multiple allotropes in the solid phase, but one liquid and gas form.
Examples of Allotropes
- White phosphorus
- Red phosphorus
- Black phosphorus