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8.4The Periodic Table

Transition elements — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions

5 min read 11 parts Lesson 4 of 5 1 quiz

📚 Cambridge IGCSE Chemistry 0620 Hub / Topical Revision
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8.4 Transition elements — Notes — IGCSE Chemistry notes: Describe the position, typical and special properties of the transition elements and compare them with Group I.The transition elements are in the centre of the Periodic Table between Group II and Group III.Typical metals — …

  • Coloured compounds
  • Different charges
  • Other colours
  • Vanadium(V) oxide
  • Why useful
  • With water

Section 1 of 11Position and general properties

The transition elements are in the centre of the Periodic Table between Group II and Group III.
Typical metals
  • Typical metals lustrous, hard and strong, conduct heat and electricity, and have high melting points.
    • (except mercury, a liquid)
Compared with Group I they have much higher densities and melting points.
Examples
  • Examples iron, copper, nickel, chromium, manganese, cobalt and titanium.

Section 2 of 11Properties special to transition elements

Coloured compounds
  • Coloured compounds copper forms blue copper sulfate, black copper oxide and green copper carbonate, and copper(II) salts are blue.
Catalysts
  • Catalysts the elements or their compounds are often catalysts, for example iron in the Haber process and V2O5 in the Contact process.
Different charges
  • Different charges they form ions with different charges, for example iron forms Fe2+ and Fe3+.
Copper forms Cu+ and Cu2+.

Section 3 of 11Variable oxidation numbers (Supplement)

1
Transition elements can lose different numbers of electrons.
2
Iron forms iron(II), Fe2+, with oxidation number +2.
3
Iron also forms iron(III), Fe3+, with oxidation number +3.
4
The Roman numeral in the name gives the oxidation number.
5
FeCl2 is iron(II) chloride and FeCl3 is iron(III) chloride.
6
Cu2O is copper(I) oxide and CuO is copper(II) oxide.
7
Compounds with different oxidation numbers have different properties and colours.

Section 4 of 11Colours of some ions

IonColour
Copper(II), Cu2+Blue
Iron(II), Fe2+Pale green
Iron(III), Fe3+Yellow-brown
  • Other colours
    • manganate(VII) is purple and chromium(III) compounds are green.

Section 5 of 11Catalysts and uses

Catalysts and uses
Iron
  • Iron the catalyst in the Haber process for ammonia.
Vanadium(V) oxide
  • Vanadium(V) oxide the catalyst in the Contact process for sulfuric acid.
Nickel
  • Nickel the catalyst for the hydrogenation of alkenes in making margarine.
Platinum
  • Platinum used in catalytic converters.
Why useful
  • Why useful transition metals can change oxidation state and provide a surface for reactions.
Iron
  • Iron used in steel for construction.
Copper
  • Copper used for electrical wiring and pipes, because it is a good conductor and malleable.
Titanium
  • Titanium used for aircraft parts, because of its strength and low reactivity.
Pigments
  • Pigments coloured compounds are used in pigments, glass and ceramics.

Section 6 of 11Transition elements compared with Group I

PropertyTransition elementsGroup I metals
DensityHighLow (float on water)
Melting pointHigh (except mercury)Low
Hardness and strengthHard and strongSoft, cut with a knife
Reactivity with water and oxygenSlow or noneVery reactive
CompoundsColouredWhite
IonsVariable chargesAlways 1+

Section 7 of 11Reactions of transition metals

With water
  • With water the reaction is very slow for most, but iron reacts with steam to form iron oxide and hydrogen.
Copper
  • Copper it does not react with water or dilute acids because it is below hydrogen in the reactivity series.
Hydroxide precipitates
  • Hydroxide precipitates adding sodium hydroxide gives coloured precipitates: blue Cu(OH)2, green Fe(OH)2 and red-brown Fe(OH)3.
Iron(II)
  • Iron(II) it is oxidised to iron(III) in air, so a green precipitate may slowly turn brown.

Section 8 of 11Exceptions

Exceptions
Scandium and zinc are in the transition region but are not considered transition elements.
They do not form coloured compounds.
They have only one oxidation state.

Section 9 of 11More from the specification

1Transition metal trends and electronic shells
  • Transition metal trends and electronic shells progressive filling of inner 3d electron shells explains unique catalytic properties and dense solid metal structures.
2Noble gases
  • The Group 0 elements, which are unreactive monatomic gases
3General Physical Properties of Transition Metals
  • Transition elements are typical hard, dense metals with high melting points, high densities,
    • and superior mechanical strength compared to Group I metals.
4Variable Oxidation States and Coloured Compounds
  • Transition metals exhibit multiple stable oxidation states (e.g. Fe2+ and Fe3+, Cu+ and Cu2+) and form brightly coloured coordination complexes and solutions.
5Catalytic Applications of Transition Metals and Compounds
  • Transition elements frequently act as catalysts in industrial processes: finely divided iron catalyzes the Haber process, vanadium(V) oxide catalyzes the Contact process,
    • and nickel catalyzes alkene hydrogenation.
6Aqueous
  • Dissolved in water.
7Displacement
  • A reaction in which a more reactive element takes the place of a less reactive one in a compound.
8Shell
  • An energy level around the nucleus that holds a limited number of electrons.
9Displacement reaction
  • A more reactive element replaces a less reactive one in a compound
10Alkali metals
  • The Group I metals, which form alkaline solutions with water.
11Outer shell
  • Highest-energy occupied shell.
12Physical property
  • A property observed or measured without changing the material.
13Halogens
  • Group 17 non-metals that form diatomic molecules.
14Halogen
  • A Group VII non-metal with seven outer electrons.
15Trend
  • General pattern down a group or across a period.
16Observation
  • What is seen, heard, smelt or measured

Section 10 of 11Key terms

TermMeaning
Transition elementa metal in the central block of the Periodic Table with variable oxidation numbers and coloured compounds.
Oxidation numberthe charge-like number showing electrons lost or gained by an atom in a compound.
Catalysta substance that speeds up a reaction and is not used up.
Roman numeralthe numeral in a name showing the oxidation number of the metal.
Variable oxidation numberthe ability to form ions with different charges.

Section 11 of 11Exam technique

1
Saying transition metals form ions with a fixed charge: they have variable oxidation numbers.
2
Mixing up copper(II) blue with iron(II) green.
3
Including zinc as a transition elementit forms no coloured compounds and has one oxidation state.
4
Saying transition metals are soft and reactive like Group I: they are hard, dense and less reactive.
5
Saying all transition metals are magnetic — only iron, cobalt and nickel are

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