SPEC 4.1.3.1–4.1.3.2 • CHEMISTRY ONLY
Properties of Transition Metals
The d-block elements — harder, denser, less reactive than Group 1, with three special chemical properties: variable oxidation states, coloured compounds, and use as catalysts.
Transition Metals — Where They Sit Chem only
Transition metals occupy the central block of the periodic table — the d-block — sandwiched between Group 2 and Group 3. They are all metals, with similar properties that distinguish them from Group 1.
Transition Element
A metal found in the central block of the periodic table (the d-block) — properties are distinct from Group 1: harder, denser, higher melting points, and far less reactive.
Chemistry Only Topic
This lesson covers content from spec sections 4.1.3.1 and 4.1.3.2, which is examined only on the GCSE Chemistry papers (8462). Combined Science Trilogy students do not sit this content. Higher Tier and Foundation Tier both cover it.
Locating the d-Block
The d-block sits between Group 2 and Group 3, starting from Period 4. The diagram below shows Period 4 of the periodic table — the row where transition metals first appear:
PERIOD 4 (atomic numbers 19–36)
← Group 1 / 2 → ← Transition metals (d-block, 10 elements) → ← Groups 3 / 4 / 5 / 6 / 7 / 0 →
s-block (Groups 1–2)
d-block (transition metals)
p-block (Groups 3–0)
Vanadium (V) — example
Examiner Alert (P2 Jun24 Q07.5)
Only ~25% of students could correctly identify vanadium (V) as a transition metal. If you're given an unfamiliar element name and need to decide whether it's a transition metal, find it on the periodic table — if it's in the central block (between Group 2 and Group 3), it's a transition metal.
Common Transition Metals to Know
The spec lists six transition metals as the examples you should know — all from Period 4 of the d-block.
SymbolNameCommon use / association
CrChromiumStainless steel; chrome plating
MnManganeseSteel hardening; MnO₂ as catalyst
FeIronConstruction; Haber process catalyst
CoCobaltMagnetic alloys; blue pigments
NiNickelCoins, batteries; hydrogenation catalyst
CuCopperWiring (electrical conductor); plumbing
Memory Hint
The spec example list is Cr, Mn, Fe, Co, Ni, Cu — six adjacent elements in Period 4. Memorise them in order; they're in the order they appear left-to-right on the periodic table.
Physical Properties vs Group 1
The spec asks specifically about FOUR physical properties for the comparison: melting point, density, strength, and hardness. Plus reactivity (chemical) but that's a separate question.
PropertyTransition metalsGroup 1 metals
Melting pointHigh (Fe = 1538 °C)Low (Na = 98 °C)
DensityHigh (Cu = 8.96 g/cm³)Low (Li, Na, K all float on water)
StrengthStrongWeak / soft
HardnessHardSoft (cut with a knife)
Reactivity (chemical)Less reactive — react slowly with O₂, water, halogensVery reactive — react vigorously
Mercury — The Exception
Almost all transition metals (and metals generally) are solid at room temperature. Mercury (Hg) is the famous exception — it's the only metal that is liquid at room temperature (mp −39 °C). Mercury is in the d-block (Period 6).
Three Special Chemical Properties
Transition metals have three distinctive chemical properties that you need to remember — none of which apply to Group 1 metals.
Property 1
Variable oxidation states
Form ions with more than one charge. E.g. iron: Fe²⁺ and Fe³⁺; copper: Cu⁺ and Cu²⁺.
Property 2
Coloured compounds
Compounds and solutions are distinctively coloured. E.g. Cu²⁺(aq) is blue; Fe²⁺(aq) is pale green.
Property 3
Useful as catalysts
Many transition metals (or their compounds) speed up reactions. E.g. Fe in the Haber process; Ni in hydrogenation.
Element vs Compound
Transition metal compounds are coloured (e.g. blue copper sulfate). The pure metal element itself is silvery / metallic looking — copper looks pinkish-orange because of its surface. Don't write "transition metals are coloured" — write "transition metal compounds are coloured".
Variable Oxidation States
Group 1 metals always form 1+ ions. Group 2 always form 2+. Transition metals can form ions with different charges — this is their first distinctive chemical property.
ElementPossible ion chargesExample compound colours
Iron (Fe)Fe²⁺ and Fe³⁺FeSO₄ = pale green; FeCl₃ = yellow-brown
Copper (Cu)Cu⁺ and Cu²⁺Cu₂O = red/brown; CuSO₄ = blue
Why Compounds Have Different Colours
The same element with different ion charges produces different colours. Iron(II) — Fe²⁺ — compounds tend to be pale green; iron(III) — Fe³⁺ — compounds tend to be yellow-brown or rust-coloured. The (II)/(III) in Roman numerals tells you the charge of the metal ion.
Spec Canonical Examples
The two examples you'll see most often in mark schemes are Fe²⁺/Fe³⁺ and Cu⁺/Cu²⁺. Other transition metals (e.g. manganese, chromium) also show variable behaviour but at GCSE the focus is on these two clean cases.
Coloured Compounds
The colours of transition metal compounds are a useful identification clue. The same metal can have different colours in different compounds (because of different oxidation states).
Compound / IonColourNotes
Cu²⁺(aq) — e.g. CuSO₄(aq)BlueThe classic "blue copper sulfate" of GCSE chemistry
Fe²⁺(aq) — iron(II)Pale greenFeSO₄ solution; iron in the +2 state
Fe³⁺(aq) — iron(III)Yellow / brownFeCl₃ solution; iron in the +3 state
MnO₄⁻(aq) — permanganatePurpleKMnO₄ — used as oxidising agent
Compare with Group 1
Group 1 compounds are white solids and colourless solutions. NaCl, KBr, LiOH — all white as solid, all colourless dissolved. The colour distinction is one of the easiest ways to tell a Group 1 from a transition metal compound.
Useful as Catalysts
Catalyst
A substance that speeds up the rate of a chemical reaction without being used up itself. (Catalysts are covered in detail in Module 6 — Rates of Reaction.)
Many transition metals (and their compounds) are excellent catalysts — used in industry to make reactions economical. Four classic examples:
CatalystProcessWhat it makes
Iron (Fe)Haber processAmmonia (NH₃) — for fertilisers
Nickel (Ni)Hydrogenation of alkenesMargarine (saturated fats from vegetable oils)
MnO₂Decomposition of H₂O₂Oxygen + water
V₂O₅Contact processSulfur trioxide (SO₃) — for sulfuric acid
Past Paper Pattern (P2 Jun24 Q07.5)
"Which is the most likely metal in the metal oxide catalyst?" — given options Al, Ba, K, V. Answer: vanadium (V) — the only transition metal in the list. Catalyst questions often hinge on identifying which metal is a transition metal.
Examiner Alert — Physical vs Chemical
Examiner Alert (P1 Jun22 Q01.3)
The question asks for PHYSICAL property differences. Many students gave chemical properties (reactivity, ions, coloured compounds) — and the mark scheme explicitly says "ignore references to chemical properties". Match your answer to the question's category.
Physical Properties
Melting point / boiling point
Density
Strength
Hardness
Malleability / ductility
Electrical conductivity
State at room temperature
Chemical Properties
Reactivity (with O₂, water, acids, halogens)
Ion charges formed
Colour of compounds
Use as catalyst
Type of bonding formed
What products form in reactions
Quick Test
If a property can be measured without a chemical reaction, it's physical. If you need a reaction to observe it, it's chemical. Melting an ice cube is physical; burning it... well, you can't burn ice cubes — that test fails for water but not for sodium.
Examiner Alert — Comparison Format
Examiner Alert (P1 Jun22 Q01.3)
"Compare" questions need both sides of the comparison. Saying "transition metals are harder" describes one side. Saying "transition metals are harder than Group 1" gives the comparison.
✗ Loses Mark
"Transition metals have higher melting points."
Property described, but the comparison side (Group 1) is missing.
✔ Wins Mark
"Transition metals have higher melting points than Group 1 metals." Or: "Group 1 metals have lower melting points than transition metals."
Mark scheme allows "converse statements" — describe Group 1's lower property as a valid alternative.
Template Sentences
"Transition metals are X, whereas Group 1 metals are Y." Or: "Group 1 metals have lower X (than transition metals)." Both formats work and meet the comparison requirement.
Practice Question 1
two
2 MARKS
Source: P1 Jun22 Q01.3 (verbatim)
P
Mark scheme — any two from (Group 1 elements): have lower melting / boiling points; have lower densities; are less strong; are softer. Converse statements (TMs higher mp etc.) accepted. [1 mark each]
E
Example pair: "(1) Group 1 metals have lower melting points than transition metals. (2) Group 1 metals are softer than transition metals." [2 marks]
E
The mark scheme explicitly IGNORES: "transition elements form coloured compounds" / "transition elements form ions with different charges" / any reference to chemical properties — those are chemical, not physical.
Practice Question 2
1 MARK
Source: based on P1 Jun22 Q01.2 (original references Figure 1 with unlabelled regions A–D on a periodic table image)
P
Answer: B (transition metals).[1 mark]
E
Why: Forming more than one ion charge (R²⁺ AND R³⁺) is the defining feature of transition metals — variable oxidation states.
E
Why not the others: Group 1 = always 1+ (one charge); Group 7 = always 1− (one charge); non-metals don't typically form 2+ or 3+ ions in this way. Only transition metals (Cr²⁺/Cr³⁺, Fe²⁺/Fe³⁺, etc.) match the description.
Practice Question 3
metal oxide
1 MARK
Tick one: Aluminium (Al) | Barium (Ba) | Potassium (K) | Vanadium (V).
Source: P2 Jun24 Q07.5 (verbatim)
P
Answer: Vanadium (V).[1 mark]
E
Why: Catalysts are typically transition metals (or their compounds). Vanadium is in the d-block (between Group 2 and Group 3) — the only transition metal in the four options.
E
Why not the others: Aluminium (Group 3, p-block) — not a transition metal. Barium (Group 2, s-block) — not a transition metal. Potassium (Group 1, s-block) — not a transition metal.
P
Real-world context: V₂O₅ is the catalyst used in the Contact process for making sulfuric acid (SO₂ → SO₃). Only ~25% of students got this question right because they couldn't locate vanadium in the d-block.
Common Errors — Quick Check
If a sentence on your answer matches the left column, swap it for the right one.
Loses the markWins the mark
"Transition metals are harder" (no comparison)"Transition metals are harder than Group 1 metals "
"Transition metals are more reactive" (when asked for PHYSICAL properties)"Transition metals have higher melting points / densities " (physical only)
"Transition metals are coloured""Transition metal compounds are coloured" (the metal element is silvery)
"Transition metals form coloured compounds" (when asked for PHYSICAL properties)Save for chemical-properties questions; mark scheme ignores this for physical-property questions
"Vanadium is an alkali metal / non-metal""Vanadium is a transition metal — in the d-block, between Group 2 and Group 3"
"Catalyst gets used up""Catalyst speeds up the reaction without being used up "
Summary
Where They Are (4.1.3.1)
Central d-block of the periodic table — between Group 2 and Group 3
Spec examples: Cr, Mn, Fe, Co, Ni, Cu (Period 4)
All metals — but distinct from Group 1 metals in nearly every property
Physical Properties vs Group 1 (4.1.3.1)
Higher melting point (except mercury, which is liquid)
Higher density
Stronger and harder
Less reactive — react slowly with O₂, water, halogens
Three Chemical Properties (4.1.3.2)
Variable oxidation states — multiple ion charges (Fe²⁺/Fe³⁺, Cu⁺/Cu²⁺)
Coloured compounds — Cu²⁺(aq) blue; Fe²⁺(aq) pale green; Fe³⁺(aq) yellow-brown
Useful as catalysts — Fe (Haber); Ni (hydrogenation); MnO₂ (H₂O₂); V₂O₅ (Contact)
Top Exam Tip
Three traps: (1) match physical vs chemical to the question — physical = mp, density, hardness; chemical = reactivity, ions, colour, catalysts. (2) Comparisons need both sides: "TM is X whereas G1 is Y". (3) Distinguish element (silvery) from compound (coloured). Locating an unfamiliar transition metal? Look for the central block of the periodic table.
Next: Transition Metals — Where They Sit Chem only