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Characteristics of transition series; first-row configuration

Short answer

Characteristics: hard and dense, high melting points, variable oxidation states, colored ions, paramagnetism, form complexes and alloys, catalytic activity. Electronic configuration: electrons fill 3d after 4s, general [Ar]3d¹⁻¹⁰4s¹⁻²; exceptions Cr [Ar]3d⁵4s¹ and Cu [Ar]3d¹⁰4s¹ due to stable half-filled and full d subshells.

Give the important characteristics of transition series. Explain the electronic configuration of first transition elements.

Important characteristics

  1. Hard, dense metals with high melting and boiling points and good electrical conductivity.
  2. Variable oxidation states (Mn: +2 to +7).
  3. Form coloured ions because of d–d transitions.
  4. Paramagnetic due to unpaired d electrons.
  5. Form many stable complexes (e.g. [Fe(CN)₆]⁴⁻).
  6. Act as catalysts (Fe, Ni, V₂O₅).
  7. Form alloys and interstitial compounds.

Electronic configuration of the first transition series

Electrons are added to 3d after 4s is filled. Configurations are [Ar] 3d¹⁻¹⁰ 4s¹⁻²:

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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