Almost all the metallic elements between Groups III to XII in the Periodic Table that have an incomplete inner electron shell and that serve as transitional links between the most and the least electropositive in a series of elements. They are characterized by the multiple valences, colored compounds, and the ability to form stable complex ions is termed to be transition metal.
Since they possess the properties of metals, the transition elements are also termed as the transition metals. Transition elements are very tough, with greater melting points & boiling points. Shifting from left to right across the periodic table, the five d orbital turn into more filled. These d electrons are very loosely bounded and which contributes to the high electrical conductivity & malleability of these elements. The transition elements have short ionization energies and also they exhibit a wide range of oxidation states or positively charged forms. The positive oxidation state allows the transition elements to form many unlike ionic and partially ionic compounds. The structure of the complexes causes the d orbitals to split into 2 energy sublevels, which makes many of the complexes to suck up the specific frequencies of light and forming the characteristic colored solutions and compounds. These complexes reactions occasionally enhance the relatively low solubility of various compounds.