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Transition elements; first series configuration

Short answer

Transition elements have an incomplete d subshell in the atom or common ion. Zn, Cd, Hg are not typical because they have a filled d10 configuration in both, lacking variable oxidation states, colour, and paramagnetism. First row configurations: Sc [Ar]3d1 4s2, Ti 3d2 4s2, V 3d3 4s2, Cr 3d5 4s1, Mn 3d5 4s2, Fe 3d6 4s2, Co 3d7 4s2, Ni 3d8 4s2, Cu 3d10 4s1, Zn 3d10 4s2.

What are transition elements? Why are all the transition elements not considered as typical transition elements? Explain the electronic configuration of the first transition elements.

Transition elements

Elements which have an incompletely filled d subshell either in the atom or in any of their common oxidation states are called transition elements (d-block elements lying between s- and p-blocks). Examples: Ti, V, Cr, Mn, Fe, Co, Ni, Cu.

Why not all are typical

Zn, Cd and Hg have a completely filled d¹⁰ subshell in the atom and in their common oxidation state (+2), so they do not show the typical properties of transition elements: variable oxidation states, coloured ions, paramagnetism, complex formation and catalytic activity. They are not considered typical transition elements.

Electronic configuration of the first transition series

ElementZConfiguration
Sc21[Ar] 3d¹ 4s²
Ti22[Ar] 3d² 4s²
V23[Ar] 3d³ 4s²
Cr24[Ar] 3d⁵ 4s¹ (exception)
Mn25[Ar] 3d⁵ 4s²
Fe26[Ar] 3d⁶ 4s²
Co27[Ar] 3d⁷ 4s²
Ni28[Ar] 3d⁸ 4s²
Cu29[Ar] 3d¹⁰ 4s¹ (exception)
Zn30[Ar] 3d¹⁰ 4s²

The exceptions Cr and Cu arise because half-filled (d⁵) and fully filled (d¹⁰) subshells have extra stability (exchange energy and symmetry). General formula: (n−1)d¹⁻¹⁰ ns¹⁻².

✓ Answer checked by Claude Opus 5.5 (high effort)

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