Define transition elements. Discuss their following characteristic properties : Formation of coloured compounds

Explanation

Transition elements The elements in which last electron enters in (n-1) d-orbital are called d-block elements. These elements are generally known as transition elements as their position in periodic table is in between that of s-block (electropositive) and p-block elements. These elements make up three complete rows, i.e. 3d, 4d, 5d, and an incomplete fourth row, i.e. 6d. Their given characteristic properties are discussed below :
Formation of coloured compounds The compounds formed by the transition elements are mainly coloured in nature. The colour arises die tot he excitation of electron from d-orbitals of lower energy to d-orbitals of higher energy (d-d transition)
Atoms or ions having `d^(1) t o d^(9)` configuration are coloured, while atoms or ions having `d^(0) or d^(10)` configuration are colourless.