Catenation can be defined as the self-linking of atoms of an element to form chains and rings. This definition can be extended to include the formation of layers like two-dimensional catenation and space lattices like three-dimensional catenation. The most common examples of catenation or elements that exhibit catenation are: Carbon, Silicon, Sulphur, Boron. Catenation occurs most readily in carbon, forming covalent bonds to form longer chains and structures with other carbon atoms. This is why the vast number of organic compounds are found in nature. Carbon is best known for its catenation properties, with the analysis of catenated carbon structures in organic chemistry. All the elements of carbon family or group 4 family exhibit catenation property. The first member from the family has the highest tendency to catenate. Following is the tendency to catenate: C > Si > Ge > Sn > Pb Catenation tendency decreases down the group. This happens because the atomic size increases down the group and the strength of the covalent bond decreases. Hence, the catenation property decreases down the group.

Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of these elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner. Example: Diamond and Graphite are the allotropes of carbon.