Catenation is the linkage of atoms of the same element into longer chains. It occurs most readily in carbon, which forms covalent bonds with other carbon atoms to form longer chains and structures. e.g. pentane, butane, etc.
Anomalous behaviour of carbon
Carbon is the 1st element in the p-block family, hence its atomic number is very small i.e. 6, because of small atomic number, the size of carbon atom is very small as compared to other element in the group. So the physical and chemical properties of carbon is different than other member in the series.