AQA GCSE Chemistry 8462: Properties of transition metals – Revision Notes

These notes condense section 4.1.3 Properties of transition metals (4.1.3.1 Comparison with Group 1 elements and 4.1.3.2 Typical properties) of the AQA GCSE Chemistry (8462) specification, for teaching from September 2016 with exams from June 2018 (version 1.1). The section is in Topic 1, assessed on Paper 1 at Foundation and Higher tier. None of it is Higher tier only, and there is no required practical for it.

For full explanations and worked examples, use the transition metals study guide. Then test yourself with the transition metals practice questions. The rest of Topic 1 is in the atomic structure revision notes. The AQA GCSE Chemistry hub and the printable checklist show where this section sits in the course.

The six elements to name

Cr, Mn, Fe, Co, Ni, Cu – chromium, manganese, iron, cobalt, nickel, copper. These are the only transition metals the specification asks you to use as examples. They sit in the central block of the periodic table, between Group 2 and Group 3.

Learn the spellings. “Maganese” and “chromeium” cost marks on recall questions.

Key definitions

• Transition elements: metals in the central block of the periodic table, with similar properties to each other that are different from those of Group 1.
• Ion: a charged particle formed when an atom loses or gains electrons. A Roman numeral in a name gives the metal ion’s charge: iron(III) = Fe³⁺.
• Catalyst: a substance that changes the rate of a reaction but is not used up. It does not appear in the chemical equation.
• Density: mass per unit volume, in g/cm³. Use “denser”, not “heavier”.

4.1.3.1 Transition metals compared with Group 1

Property	Group 1 (Li, Na, K)	Transition metals (Cr–Cu)
Melting point	low: all below 200 °C	high: all six above 1000 °C
Density	low: Li, Na, K float on water	high: about 7–9 g/cm³
Strength	weak	strong
Hardness	soft, cut with a knife	hard
Reaction with oxygen	tarnish fast in air; stored under oil	slow, or only when heated
Reaction with water	react with cold water, fizz, give H₂ and an alkali	Cu: no reaction; Fe: very slow (rusting needs air too)
Reaction with halogens	vigorous, e.g. Na burns in Cl₂	less vigorous, usually need heating

Useful data (given in questions, not to memorise):

	Li	Na	K	Cr	Fe	Cu
Melting point / °C	181	98	64	1907	1538	1085
Density / g/cm³	0.53	0.97	0.89	7.15	7.87	8.96

Equations to have ready

Reaction	Group 1	Transition metal
with oxygen	4Na + O₂ → 2Na₂O	2Cu + O₂ → 2CuO (black, on heating)
with water	2K + 2H₂O → 2KOH + H₂	copper: no reaction
with chlorine	2Na + Cl₂ → 2NaCl (white)	2Fe + 3Cl₂ → 2FeCl₃ (brown, iron heated)

Method: answering a “compare” question

1. Pick one property at a time.
2. Name both metals, or use a comparative word (higher, denser, less reactive).
3. If data are given, quote a figure for each metal or work out a difference or ratio.
4. Move to the next property. Do not repeat the same property in different words.

Small reminder. “Compare chromium and potassium (melting point).” Chromium’s melting point is far higher: 1907 − 64 = 1843 °C higher. That is one property, compared and backed by data.

4.1.3.2 Typical properties

Many transition elements:

1. have ions with different charges
2. form coloured compounds
3. are useful as catalysts.

“Many”, not “all”. Group 1 metals form only 1+ ions, and their compounds are white or colourless.

Ions with different charges

Element	Ions	Example names and formulae
Fe	Fe²⁺, Fe³⁺	iron(II) sulfate FeSO₄, iron(III) chloride FeCl₃
Cu	Cu⁺, Cu²⁺	copper(I) oxide Cu₂O, copper(II) oxide CuO
Cr	Cr²⁺, Cr³⁺	chromium(III) oxide Cr₂O₃
Co	Co²⁺, Co³⁺	cobalt(II) chloride CoCl₂
Mn	Mn²⁺ and others	manganese(IV) oxide MnO₂

Method: formula from a Roman numeral

1. The numeral gives the metal ion’s charge.
2. Write the charge of the other ion (Cl⁻, O²⁻, SO₄²⁻).
3. Use enough of each ion to make total + equal total −.
4. Put brackets round a group ion if you need more than one: Fe₂(SO₄)₃.

Coloured compounds

Compound	Colour
copper(II) sulfate solution	blue
copper(II) carbonate	green
copper(II) oxide	black
iron(II) compounds	pale green
iron(III) compounds	orange-brown
chromium(III) oxide	green
potassium dichromate	orange
potassium manganate(VII)	purple
hydrated cobalt(II) chloride	pink
nickel(II) sulfate	blue-green

Link to chemical analysis (4.8.3.2): with sodium hydroxide solution, copper(II) gives a blue precipitate, iron(II) green, iron(III) brown. The colour tells you the charge on the iron ion. More in the Chemical analysis revision notes.

Catalysts

Catalyst	Reaction
iron	Haber process: N₂ + 3H₂ ⇌ 2NH₃
manganese(IV) oxide	decomposition of hydrogen peroxide: 2H₂O₂ → 2H₂O + O₂

Iron in the Haber process is the catalyst the specification names. How a catalyst works (lower activation energy) is Topic 6: see the rate and extent of chemical change revision notes.

How to recognise a catalyst in data: the reaction is faster with it, the same mass is left at the end, and it is not in the equation.

Must-know distinctions

• Less reactive (transition metals) vs more reactive (Group 1). Transition metals are not unreactive: iron rusts, and heated iron burns in oxygen.
• Dense vs heavy. Density compares equal volumes.
• Hard (resists scratching and denting) vs strong (resists breaking under force). The specification lists both, so name both.
• Iron(II) (Fe²⁺, green) vs iron(III) (Fe³⁺, orange-brown). Iron(II) does not mean “two iron atoms”.
• Catalyst (not used up, not in the equation) vs reactant (used up, in the equation).

Linking a property to a use

Exam questions often give a use and ask which property explains it. Match the use to the property, then say why Group 1 would fail.

Use	Property that matters	Why a Group 1 metal would not work
iron (as steel) in bridges and tools	strong, hard	Group 1 metals are soft and weak
copper water pipes	does not react with water	Group 1 metals react with cold water
iron catalyst in the Haber process	catalytic activity; stays solid at the process temperature of about 450 °C	sodium melts at 98 °C, so it would be liquid
coloured glazes and pigments	coloured compounds	Group 1 compounds are white

Small reminder (catalyst data). A powder speeds up a reaction, and 1.0 g is put in and 1.0 g is recovered. It is a catalyst: faster reaction and mass unchanged. If only 0.6 g were recovered, it would be acting as a reactant, because it was used up.

Quick self-test

1. Name the six transition metals the specification uses as examples.
2. State two physical properties in which iron differs from sodium.
3. Using the data table above, how many times as dense as potassium is copper? Give your answer to 2 significant figures.
4. Write the formula of copper(I) chloride.
5. Write the formula of chromium(III) chloride.
6. Write the formula of iron(III) sulfate.
7. Give the colour of potassium manganate(VII).
8. A solution gives a brown precipitate with sodium hydroxide solution. Which ion is present?
9. Balance: Fe + Br₂ → FeBr₃.
10. Name the catalyst used in the Haber process.
11. Why is copper, not potassium, used for hot water pipes? Give two reasons.
12. True or false: every transition metal compound is coloured and every transition metal is a catalyst.

Answers

1. Chromium, manganese, iron, cobalt, nickel, copper.
2. Any two: iron has a higher melting point; is denser; is harder; is stronger.
3. 8.96 ÷ 0.89 = 10.07, so about 10 times.
4. Cu⁺ and Cl⁻: CuCl.
5. Cr³⁺ and three Cl⁻: CrCl₃.
6. Two Fe³⁺ (6+) and three SO₄²⁻ (6−): Fe₂(SO₄)₃.
7. Purple.
8. Iron(III), Fe³⁺.
9. 2Fe + 3Br₂ → 2FeBr₃.
10. Iron.
11. Copper does not react with water; potassium reacts vigorously with water. Copper has a high melting point and is strong; potassium is soft and melts at 64 °C.
12. False: the specification says many transition elements have these properties, not all.

Where marks are usually lost

• Saying transition metals are “more reactive” than Group 1, or calling them “unreactive”.
• Writing “heavier” instead of “denser”.
• Describing one metal only in a “compare” question.
• Giving an example metal outside Cr, Mn, Fe, Co, Ni, Cu (or a Group 2 metal by mistake).
• Leaving the Roman numeral off iron and copper compound names.
• Swapping iron(II) green and iron(III) orange-brown.
• Writing a catalyst as a reactant in the equation.
• Claiming that all transition elements are catalysts or form coloured compounds.
• Forgetting brackets in formulae such as Fe₂(SO₄)₃.

Official syllabus

AQA GCSE Chemistry (8462) specification, for teaching from September 2016, GCSE exams June 2018 onwards, version 1.1, published by AQA – section 4.1.3 Properties of transition metals (4.1.3.1 and 4.1.3.2).