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d-block elements; 3d configuration; non-typical metals

Short answer

d-block elements have the last electron entering (n-1)d. 3d series configurations: Sc [Ar]3d¹4s² to Zn [Ar]3d¹⁰4s²; Cr [Ar]3d⁵4s¹ and Cu [Ar]3d¹⁰4s¹ are exceptions. Zn, Cd, Hg are not transition metals because their atoms and M²⁺ ions have d¹⁰, so no incomplete d-orbital; they lack variable valency and typical transition properties.

What are d-block elements? Give the electronic configuration of 3d series. Mention which d block metals are not considered as transition metals and why?

d-block elements

Elements in which the last electron enters the (n−1)d subshell. They are in groups 3 to 12 of the periodic table.

Configuration of the 3d series

Sc  [Ar] 3d¹ 4s²     Fe  [Ar] 3d⁶ 4s²
Ti  [Ar] 3d² 4s²     Co  [Ar] 3d⁷ 4s²
V   [Ar] 3d³ 4s²     Ni  [Ar] 3d⁸ 4s²
Cr  [Ar] 3d⁵ 4s¹     Cu  [Ar] 3d¹⁰ 4s¹
Mn  [Ar] 3d⁵ 4s²     Zn  [Ar] 3d¹⁰ 4s²

Cr and Cu are exceptions: a half-filled (d⁵) or completely filled (d¹⁰) 3d subshell is extra stable, so one 4s electron moves into 3d.

Metals not considered transition metals

Zn, Cd and Hg (group 12). Their atoms and common ions (M²⁺) have a completely filled d¹⁰ subshell, so they have no incomplete d orbital in any common state. They do not show typical transition properties: no variable valency, colourless diamagnetic compounds, and low melting points (Hg is liquid). Sc is sometimes also named, as Sc³⁺ has a d⁰ configuration.

✓ Answer checked by Claude Opus 5.5 (high effort)

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