What Is a Transition Metal?
Transition metals are d-block elements between the second and third groups in the periodic table. Examples of well-known transition metals include titanium, iron, nickel, and copper. They are unique from other elements due to their ability to form an incomplete d sub-shell in the form of at least one ion.
Although scandium and zinc are found within the d-block of the periodic table, they are not in fact usually classified as transition metals because they do not fully fulfil the necessary criteria. This is due to the fact that scandium can only form one ion with a charge of 3+, but with d orbitals that have no electrons occupying them; zinc on the other hand can only form an ion with a charge of 2+, but with electrons that fully occupy its d-orbitals.