allotróp

An allotróp refers to one of two or more distinct forms of a chemical element that exist in the same physical state (solid, liquid, or gas) but differ in their atomic arrangement and, consequently, in their physical and chemical properties. The term originates from the Greek words *allos*, meaning "other," and *tropos*, meaning "form." Allotropy is a specific case of polymorphism, where substances can exist in multiple crystalline or amorphous forms.

The most well-known example of allotropy is carbon, which exhibits several allotropes, including diamond, graphite, and graphene. Diamond is a hard, transparent crystal with a three-dimensional network of carbon atoms, while graphite consists of layered sheets of carbon atoms arranged in a hexagonal lattice, giving it a soft, slippery texture. Another allotrope, graphene, is a single layer of carbon atoms arranged in a two-dimensional honeycomb structure, renowned for its exceptional strength and electrical conductivity.

Oxygen and sulfur are additional elements that display allotropy. Oxygen exists as dioxygen (O₂), a gas at standard conditions, and as ozone (O₃), a less stable allotrope with a distinct blue color and stronger oxidizing properties. Sulfur forms several allotropes, including the cyclic S₈ ring structure (common in elemental sulfur) and plastic sulfur, which is a polymerized form with different physical properties.

Allotropes can influence an element’s reactivity, density, electrical conductivity, and other properties. For instance, graphite conducts electricity due to its delocalized electrons, whereas diamond is an insulator. The existence of allotropes is crucial in materials science, chemistry, and engineering, as they enable the development of specialized materials tailored for specific applications.