The Transition Elements T
The transition elements (transition metals) occupy the central block of the periodic table, between Groups 2 and 3. They are all metals with several distinctive properties that set them apart from the Group 1 and Group 2 metals.
Properties of Transition Metals
| Property | Detail |
|---|---|
| Density | High densities |
| Melting points | High melting points — exception: mercury (Hg) is a liquid at room temperature (m.p. = −39 °C) |
| Strength | Hard and strong |
| Malleability | Malleable and ductile — can be shaped and drawn into wire |
| Conductivity | Good conductors of heat and electricity |
| Reactivity | Less reactive than Group 1 alkali metals — do not react vigorously with water or oxygen at room temperature |
| Compounds | Form coloured compounds (e.g. copper(II) sulfate is blue, iron(III) oxide is red-brown, potassium manganate(VII) is purple, chromium(III) compounds are green, cobalt(II) chloride is pink) |
| Ion charges | Can form ions with different charges (variable oxidation states) — e.g. Fe²⁺ and Fe³⁺ |
| Catalysts | Transition metals and their compounds are widely used as catalysts |
AQA names six transition metals to illustrate these properties: chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) — you should be able to use these as your examples.
Transition Metals vs Group 1 Alkali Metals
The transition metals are very different from the Group 1 alkali metals. You need to be able to describe and explain these differences:
| Property | Transition metals | Group 1 alkali metals |
|---|---|---|
| Melting points | High — e.g. iron melts at 1538 °C | Low — e.g. lithium melts at 181 °C |
| Reactivity | Much less reactive — iron does not react with cold water | Very reactive — react vigorously with cold water |
| Reaction with oxygen & halogens | React slowly — e.g. iron oxidises (rusts) only slowly; react with halogens when heated | React vigorously — burn readily in oxygen and react rapidly with halogens to form salts |
| Hardness & strength | Hard and strong | Soft — can be cut with a knife |
| Density | High densities | Low densities — Li, Na and K are less dense than water |
Variable Ion Charges
Unlike Group 1 metals (always +1) and Group 2 metals (always +2), transition metals can form ions with different positive charges. The charge is shown by a Roman numeral:
| Ion | Symbol | Example compound |
|---|---|---|
| Iron(II) | Fe²⁺ | Iron(II) chloride, FeCl₂ |
| Iron(III) | Fe³⁺ | Iron(III) oxide, Fe₂O₃ (rust) |
| Copper(II) | Cu²⁺ | Copper(II) sulfate, CuSO₄ (blue) |
| Chromium(III) | Cr³⁺ | Chromium(III) oxide, Cr₂O₃ (green) |
| Manganese(IV) | Mn⁴⁺ | Manganese(IV) oxide, MnO₂ |
Transition Metals as Catalysts(Useful context, not required knowledge)
| Catalyst | Industrial process |
|---|---|
| Iron (Fe) | Haber process — production of ammonia |
| Platinum (Pt) | Ostwald process — production of nitric acid |
| Nickel (Ni) | Hydrogenation of vegetable oils (making margarine) |
Uses of Key Transition Metals (Useful context, not required knowledge)
| Metal | Uses | Relevant property |
|---|---|---|
| Iron (Fe) | Steel (bridges, vehicles, tools, buildings) | Strong; forms alloy with carbon |
| Copper (Cu) | Electrical cables; water pipes | Excellent conductor; malleable; resists corrosion |
| Titanium (Ti) | Aircraft components; artificial hip joints; nuclear power station pipes | Low density; high strength; corrosion-resistant; biocompatible |
Give three properties that transition metals share. Explain, using two specific properties, why copper is a suitable material for electrical cables.
Show answer
Three properties (any three from):
- High melting points
- High density / hard and strong
- Good conductors of heat and electricity
- Less reactive than alkali metals
- Form coloured compounds
- Variable ion charges / act as catalysts
Why copper for electrical cables: Copper is an excellent conductor of electricity, so current passes through it easily. It is also malleable and ductile, so it can be drawn into thin wires. Its relative unreactivity means it does not corrode quickly.
🧪 Exam-style questions Triple
Which property is typical of a transition metal but not of a Group 1 metal? Tick (✓) one box.
Describe three ways in which the transition metals differ from the Group 1 metals.
Show answer
Any three from 3 marks (1 mark each):
- Transition metals have higher melting points (Group 1 melt easily / have low melting points)
- Transition metals are harder and stronger (Group 1 are soft)
- Transition metals have higher densities
- Transition metals are less reactive (e.g. react slowly or not at all with water)
- Transition metals form ions with different (variable) charges (Group 1 always form 1+)
- Transition metals form coloured compounds (Group 1 compounds are white/colourless)
- Many transition metals / their compounds are useful as catalysts
Explain why copper is a suitable metal for electrical wiring.
Show answer
- Copper is a good (electrical) conductor, so the current passes through it easily 1 mark
- It is ductile, so it can be drawn into thin wires (and it does not corrode / react easily) 1 mark