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Transition elements; why so called; 3d configurations

Short answer

Transition elements are d-block elements with partly filled d-subshell in neutral or ionic state. They are so called as they bridge highly electropositive s-block and electronegative p-block, showing transitional properties. Electronic configurations: Sc [Ar]3d¹4s² to Zn [Ar]3d¹⁰4s²; exceptions Cr [Ar]3d⁵4s¹ and Cu [Ar]3d¹⁰4s¹ due to extra stability of half-filled and fully filled d subshells.

What are transition elements? Why are they so called? Write down the electronic configurations of 3D series.

Transition elements

Transition elements are the d-block elements that have a partly filled d-subshell in the atom or in at least one of their common oxidation states. The 3d series is Sc to Zn (general outer configuration (n−1)d¹⁻¹⁰ ns¹⁻²).

Why so called

They are placed between the s-block (highly electropositive) and p-block (electronegative) elements, and their properties are transitional between the two. Their atoms or ions have incompletely filled d orbitals.

Configurations 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.

✓ Answer checked by Claude Opus 5.5 (high effort)

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