Why is scandium not a transition metal?

It forms only Sc³⁺, which is [Ar] and has no d electrons.

Why is zinc not a transition metal?

It forms only Zn²⁺, which is [Ar]3d¹⁰ with a full d-subshell.

Why is copper a transition metal?

It forms Cu²⁺, [Ar]3d⁹, which has an incomplete d-subshell.

Give the electronic configuration of a chromium atom.

1s²2s²2p⁶3s²3p⁶3d⁵4s¹

Give the electronic configuration of a copper atom.

1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹

Why are the Cr and Cu configurations unusual?

A half-full (3d⁵) or full (3d¹⁰) subshell is a more stable arrangement.

Why do transition metals show variable oxidation numbers?

The 3d and 4s subshells are close in energy, so both can lose electrons or be used in bonding.

Why does calcium show only the +2 oxidation number?

The third electron would come from the inner 3p subshell, needing a much larger energy.

Properties of transition metalsEdexcel 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 an incomplete d-subshell.
Why is scandium not a transition metal?: It forms only Sc³⁺, which is [Ar] and has no d electrons.
Why is zinc not a transition metal?: It forms only Zn²⁺, which is [Ar]3d¹⁰ with a full d-subshell.
Why is copper a transition metal?: It forms Cu²⁺, [Ar]3d⁹, which has an incomplete d-subshell.
Give the electronic configuration of a chromium atom.: 1s²2s²2p⁶3s²3p⁶3d⁵4s¹
Give the electronic configuration of a copper atom.: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹
Why are the Cr and Cu configurations unusual?: A half-full (3d⁵) or full (3d¹⁰) subshell is a more stable arrangement.
Which electrons are lost first when a d-block atom forms an ion?: The 4s electrons.
Give the electronic configuration of Fe³⁺.: [Ar]3d⁵
Give the electronic configuration of Cu²⁺.: [Ar]3d⁹
Give the electronic configuration of V³⁺.: [Ar]3d²
Why do transition metals show variable oxidation numbers?: The 3d and 4s subshells are close in energy, so both can lose electrons or be used in bonding.
Why does calcium show only the +2 oxidation number?: The third electron would come from the inner 3p subshell, needing a much larger energy.

Exam questions on Properties of transition metals

A student is classifying the period 4 d-block elements, from scandium (Z = 21) to zinc (Z = 30), using their atomic numbers.
Explain why scandium is a d-block element but is not classified as a transition metal.2 marks
Copper (Z = 29) is used in electrical wiring and forms compounds containing Cu⁺ ions and Cu²⁺ ions.
Cu⁺ ions have a full 3d subshell. Explain why copper is nevertheless classified as a transition metal.2 marks
Vanadium (Z = 23) forms compounds in which its oxidation number is +2, +3, +4 or +5, for example in VO₂⁺, which contains vanadium(V). Calcium (Z = 20) forms compounds in which its oxidation number is only +2.
Deduce the full electronic configuration of a vanadium atom and of a V³⁺ ion, and state the number of 3d electrons in the vanadium in VO₂⁺.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).