Introduction to Transition Metals

The transition metals occupy the central block of the periodic table, spanning Groups 3 to 12 in Period 4 (and further periods below). For Edexcel A-Level, the focus is on the first-row transition metals from scandium (Sc) to zinc (Zn), with particular attention to the elements titanium through copper.

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Defining a Transition Metal

The A-Level definition of a transition metal is precise and frequently tested:

A transition metal is a d-block element that forms at least one stable ion with an incomplete d sub-shell.

This definition is important because it excludes two d-block elements from the transition metal category:

• Scandium (Sc): Its only stable ion is Sc³⁺, which has the electron configuration [Ar] — no d electrons at all. The d sub-shell is empty, not incomplete.
• Zinc (Zn): Its only stable ion is Zn²⁺, which has the configuration [Ar] 3d¹⁰ — a completely full d sub-shell, not incomplete.

All other first-row d-block elements (Ti, V, Cr, Mn, Fe, Co, Ni, Cu) form ions with partially filled d sub-shells and are therefore transition metals.

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Electron Configurations of the First-Row d-Block