The transition metals are the elements of Groups 3 to 12 belonging to the periods 4 to 7 located as d – block elements of the periodic table. The properties of these elements are in between s–block and p–block elements i.e., d–block elements represent change or transition in properties from most electropositive s–block elements to least electropositive p–block elements. Therefore these are called as transition elements.

Previously transition elements regarded as those elements which have partially filled penultimate d–orbitals in their ground state or in one of the common oxidation state. This definition included coinage metals (copper, silver, gold) in the transition elements since their di positive ions have partially filled d–sub shells.

However, the above definition does not cover the elements of Group 12, i.e., zinc metals (zinc, cadmiun, mercury) as these elements do not posses partially filled d–sub shells either in the ground state or in ions.

However, zinc metals showing similarities in some of chemical properties with transition metals are included in this block. These are considered as the end members of transition series in order to maintain rational classification of elements.

All d–block elements exhibit (n–1) d^1–10 ns^1–2 electronic configuration. Some characteristic features of the electronic configurations of the transition elements are;

Atoms of all transition elements consist of an inner core of electrons having noble gas configuration.
For example, Sc: [Ar]3d¹⁴s², Y: [Kr]4d¹5s², La: [Xe]5d¹6s². The half–filled and completely filled d–orbitals gain extra–stability. So, such configurations are favored wherever possible.

The d–block transition elements are classified as First, second, third and fourth transition series elements.

The transition metal compounds exhibit colors due to d–d transitions and charge transfer transitions. For example manganese compound KMnO₄ and chromium compound K₂Cr₂O₇ exhibits purple and orange colors respectively , both are good oxidizing agents.

Transition metals are good conductors of heat and electricity.

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