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1.3.2 Typical properties

1.3.2 Typical properties of transition metals

Transition metals form ions with different charges

Definition

Transition element

An element in the central block of the periodic table that has typical metallic properties and often forms coloured compounds and ions with different charges.

  1. Unlike Group 1 metals, which only form +1+1+1 ions, transition metals can form ions with more than one charge.
  2. The charges these metals can form are:
    1. Chromium: +2,+3,+4,+5,+6+2, +3, +4, +5, +6+2,+3,+4,+5,+6.
    2. Manganese: +2,+3,+4,+5,+6,+7+2, +3, +4, +5, +6, +7+2,+3,+4,+5,+6,+7.
    3. Iron: +2,+3,+4,+5,+6+2, +3, +4, +5, +6+2,+3,+4,+5,+6.
    4. Cobalt: +2,+3,+4,+5+2, +3, +4, +5+2,+3,+4,+5.
    5. Nickel: +2,+3,+4+2, +3, +4+2,+3,+4.
    6. Copper: +1,+2,+3+1, +2, +3+1,+2,+3.
  3. The charge is shown by a Roman numeral, such as iron(II) Fe2+\text{Fe}^{2+}Fe2+ and iron(III) Fe3+\text{Fe}^{3+}Fe3+.
Key Idea
  • Forming ions of different charges (variable charge) is a key feature of transition metals.
  • At GCSE the ones you must know are Fe2+\text{Fe}^{2+}Fe2+ and Fe3+\text{Fe}^{3+}Fe3+ and Cu2+\text{Cu}^{2+}Cu2+; the fuller lists show the range that is possible.

Different charges give differently coloured compounds

Definition

Compound

A substance containing atoms of two or more different elements chemically bonded together.

  1. Transition metals form coloured compounds, while Group 1 compounds are usually white.
  2. The colour depends on the metal ion and on its charge, so one metal can give several colours:
    1. Chromium: +2+2+2 blue, +3+3+3 green, +6+6+6 orange.
    2. Manganese: +2+2+2 pale pink, +4+4+4 brown-black, +6+6+6 green, +7+7+7 purple.
    3. Iron: +2+2+2 pale green, +3+3+3 reddish brown.
    4. Cobalt: +2+2+2 pink, +3+3+3 green.
    5. Nickel: +2+2+2 green.
    6. Copper: +2+2+2 blue.
Note

The colour is a quick way to identify the metal ion in a compound.

Uses as catalysts

  1. Many transition metals and their compounds are useful catalysts, which speed up reactions without being used up.
  2. Manganese(IV) oxide catalyses the decomposition of hydrogen peroxide:
    1. 2H2O2ā†’2H2O+O22\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_22H2ā€‹O2ā€‹ā†’2H2ā€‹O+O2ā€‹
  3. Iron catalyses the Haber process, which makes ammonia:
    1. N2+3H2ā‡Œ2NH3\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3N2ā€‹+3H2ā€‹ā‡Œ2NH3ā€‹
  4. Nickel catalyses hydrogenation, used in the manufacture of margarine by adding hydrogen to the C=C double bonds in oils.
Self review
  • Give the ion charges that iron and copper commonly form.
    • Answer: iron +2+2+2 and +3+3+3; copper mainly +2+2+2.
  • Why can one transition metal give several colours of compound?
    • Answer: the colour depends on the charge of the metal ion, and the metal can form ions of different charges.
  • Which catalyst is used for the decomposition of hydrogen peroxide?
    • Answer: manganese(IV) oxide.
  • Give the catalyst and use for the Haber process and for margarine.
    • Answer: iron for the Haber process, nickel for making margarine by hydrogenation.
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Concept map linking transition metal compounds to variable charges, coloured compounds and catalyst examples

Transition elements are the metals in the central block of the periodic table. At GCSE, the most useful examples here are chromium, manganese, iron, cobalt, nickel and copper.

When exam questions ask for their typical properties, think "charges, colours, catalysts". Many transition metal compounds show variable charges, many are coloured, and some are useful catalysts.

A compound contains chemically joined elements, and many transition metal compounds are ionic. That means they contain positive metal ions such as Fe2+Fe^{2+}Fe2+ or Cu2+Cu^{2+}Cu2+ paired with negative ions.

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What charge pattern distinguishes transition metals from Group 1 metals?

1.3.2 Typical properties Revision Guide

  1. GCSE
  2. /Chemistry
  3. /1.3.2 Typical properties

Revision notes for AQA GCSE Chemistry 1.3.2 Typical properties. Open the guide for explanations and worked examples. Written against the AQA GCSE Chemistry (8462) specification, so the content matches what's examinable rather than general Chemistry background.

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