Why is scandium not a transition metal?

Its only ion, Sc³⁺, is [Ar] and has no d electrons.

Why is zinc not a transition metal?

Its only ion, Zn²⁺, is [Ar] 3d¹⁰, a full d sub-shell.

Why is copper a transition metal?

Cu²⁺ is [Ar] 3d⁹, an incompletely-filled d sub-shell.

Which electrons are lost first when a Period 4 d-block atom forms an ion?

The 4s electrons, then the 3d electrons.

Electronic configuration of chromium?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹.

Electronic configuration of copper?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹.

Electronic configuration of Fe³⁺?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵.

Why do transition metals show variable oxidation numbers?

The 4s and 3d sub-shells are close in energy, so different numbers of electrons from both can be lost or used in bonding.

Why does calcium only form Ca²⁺?

The third electron would come from the 3p sub-shell, so the third ionisation energy is very large.

Transition metals, configurations and oxidation statesEdexcel International A Level Chemistry: Flashcards

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Define a transition metal.

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Define a transition metal.: A d-block element that forms one or more stable ions with incompletely-filled d orbitals.
Which Period 4 d-block elements are not transition metals?: Scandium and zinc.
Why is scandium not a transition metal?: Its only ion, Sc³⁺, is [Ar] and has no d electrons.
Why is zinc not a transition metal?: Its only ion, Zn²⁺, is [Ar] 3d¹⁰, a full d sub-shell.
Why is copper a transition metal?: Cu²⁺ is [Ar] 3d⁹, an incompletely-filled d sub-shell.
Which sub-shell fills first, 4s or 3d?: 4s.
Which electrons are lost first when a Period 4 d-block atom forms an ion?: The 4s electrons, then the 3d electrons.
Electronic configuration of chromium?: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹.
Electronic configuration of copper?: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹.
Electronic configuration of Fe³⁺?: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵.
Why do transition metals show variable oxidation numbers?: The 4s and 3d sub-shells are close in energy, so different numbers of electrons from both can be lost or used in bonding.
Why does calcium only form Ca²⁺?: The third electron would come from the 3p sub-shell, so the third ionisation energy is very large.

Exam questions on Transition metals, configurations and oxidation states

A technician prepares aqueous solutions of salts of Period 4 d-block metals for a titration practical and records the electronic configurations of the metal atoms and ions involved.
Deduce the full electronic configurations of an iron atom and of an Fe³⁺ ion.2 marks
Scandium, copper and zinc are all Period 4 elements in the d-block. Scandium forms only the Sc³⁺ ion in its compounds and zinc forms only the Zn²⁺ ion. Copper forms both Cu⁺ and Cu²⁺ ions.
Explain why zinc is not classed as a transition metal.2 marks
Manganese forms compounds in a wide range of oxidation states. A chemist has samples of manganese(IV) oxide, MnO₂, potassium manganate(VI), K₂MnO₄, and potassium manganate(VII), KMnO₄.
Deduce the oxidation number of manganese in MnO₂, in K₂MnO₄ and in KMnO₄.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).