What are transition elements in the context of the Periodic Table?

Transition elements, also known as transition metals, are elements found in the d-block of the Periodic Table. They are characterized by having partially filled d-orbitals. These elements include metals like iron, copper, and nickel, and are known for their ability to form various oxidation states and colored compounds. In the Cambridge IGCSE Chemistry curriculum, understanding the properties and uses of transition elements is essential.

Why do transition elements exhibit variable oxidation states?

Transition elements exhibit variable oxidation states because they have electrons in both their outermost s and d subshells that can participate in bonding. This allows them to lose different numbers of electrons, leading to multiple oxidation states. For example, iron can exist in the +2 and +3 oxidation states. This property is significant in many chemical reactions and is a key concept in the Cambridge IGCSE Chemistry syllabus.

What are some common properties of transition elements?

Common properties of transition elements include high melting and boiling points, the ability to form colored compounds, and good conductivity of heat and electricity. They are also known for their catalytic properties and the ability to form complex ions. These characteristics make them distinct from other elements in the Periodic Table and are important topics covered in the Cambridge IGCSE Chemistry course.

How do transition elements form colored compounds?

Transition elements form colored compounds due to the presence of partially filled d-orbitals. When light hits these compounds, certain wavelengths are absorbed as electrons are promoted between d-orbitals of different energy levels. The color observed is the complementary color of the absorbed light. This phenomenon is an intriguing aspect of transition metals studied in the Cambridge IGCSE Chemistry curriculum.

What role do transition elements play as catalysts in chemical reactions?

Transition elements often serve as catalysts in chemical reactions due to their ability to change oxidation states and form complex ions. This allows them to facilitate reactions by providing an alternative pathway with a lower activation energy. For instance, iron is used as a catalyst in the Haber process for ammonia production. Understanding the catalytic role of transition metals is a key part of the Cambridge IGCSE Chemistry syllabus.

Why is "Saying transition metals are soft and reactive" a common mistake in Transition Elements?

Why it happens: Generalising 'metal' from Group I. How to avoid it: Transition metals are HARD, dense and LESS reactive than Group I. Source: 0620/42 — recurring

Why is "Always writing iron as $\text{Fe}^{2+}$" a common mistake in Transition Elements?

Why it happens: Defaulting to one charge. How to avoid it: Transition metals have VARIABLE oxidation states. State which ion the question refers to.

Why is "Saying transition metal compounds are always white" a common mistake in Transition Elements?

Why it happens: Generalising from sodium chloride. How to avoid it: Transition metal compounds are typically COLOURED — the colour depends on metal AND oxidation state.

The Periodic TableCambridge IGCSE Chemistry (0620)

Transition Elements

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Transition Elements — Cambridge IGCSE 0620 Chemistry Extended (2026)

The middle block of the Periodic Table. Variable oxidation states, coloured compounds, often catalytic. Examples: iron, copper, zinc.

What you’ll learn

Mapped to the Cambridge IGCSE 0620 syllabus (2026-2028).

10.5 — Describe properties of transition metals.
10.5 — Compare transition metals with Group 1 metals.
10.5 — Recall colours of common transition metal compounds.

Common properties

High density, high m.p., variable oxidation states, often coloured, often catalytic.

Physical properties.

High density (e.g. iron $7.9\,\text{g/cm}^{3}$ , copper $8.9$ , much higher than Na $0.97$ ).
High m.p. (most $> 1000\degree\text{C}$ ; iron $1535\degree\text{C}$ ).
Hard.
Good conductors of heat and electricity.
Often shiny / lustrous.

Chemical properties.

Variable oxidation states. Iron forms Fe²⁺ AND Fe³⁺. Copper forms Cu⁺ AND Cu²⁺. Manganese can be Mn²⁺, Mn⁴⁺, Mn⁶⁺, Mn⁷⁺.
Coloured compounds. Distinctive colours arise from electronic transitions in d-orbitals.
Often catalytic. Iron (Haber), V₂O₅ (Contact), nickel (hydrogenation), platinum (cars).
Less reactive than Group 1 metals. Don't react with cold water (mostly). Iron rusts slowly in moist air; copper barely reacts.
Form complex ions. Beyond IGCSE detail, but important — coloured complexes (e.g. blue copper complexes) are studied later.

Worked qualitative. Adding sodium hydroxide to a green solution gives a green precipitate. Identify the metal ion. Most likely Fe²⁺ (forms green Fe(OH)₂ precipitate).

High density and m.p.
Variable oxidation states.
Coloured compounds.
Often catalytic.
Less reactive than Group 1.

Common colours of transition-metal compounds

Memorise the standard colours — they're the basis of qualitative testing.

Ion	Colour in solution / compound
Cu²⁺	Blue
Cu⁺	Often white / colourless
Fe²⁺	Pale green
Fe³⁺	Yellow-brown / orange
Mn²⁺	Pale pink (often appears almost colourless in dilute solution)
MnO₄⁻ (Mn $^{7+}$ )	Deep purple
Cr³⁺	Green
Cr $_{2}$ O $_{7}^{2-}$ (Cr $^{6+}$ )	Orange
Ni²⁺	Green
Co²⁺	Pink

Hydroxide precipitates.

Cu(OH)₂: blue.
Fe(OH)₂: green.
Fe(OH)₃: red-brown / rust.
Zn(OH)₂: white. (Zn IS NOT classified as transition for some Cambridge purposes — but it is in Group 12.)
Ca(OH)₂: white (not transition metal, but appears in tests).

Worked qualitative. Add NaOH to a colourless solution; a white precipitate forms; the precipitate redissolves in EXCESS NaOH. Identify the metal. Likely Zn²⁺ — Zn(OH)₂ is white and amphoteric (redissolves in excess base).

Cambridge tip. Cambridge IGCSE qualitative analysis tables identify metal ions by these colour reactions. Memorise the common ones — they appear in every Paper 4.

Cu²⁺ blue, Fe²⁺ pale green, Fe³⁺ orange.
Mn²⁺ pale pink, MnO₄⁻ deep purple.
Cr³⁺ green, dichromate orange.
Hydroxide precipitates have characteristic colours.

Transition metals vs Group 1

Transition metals: hard, dense, high m.p., less reactive, coloured. Group 1: soft, low-density, very reactive, white compounds.

Side-by-side comparison.

Property	Group 1 (alkali metals)	Transition metals
Density	Low (Li $0.5$ , Na $1.0$ , K $0.86\,\text{g/cm}^{3}$ )	High ( $> 4\,\text{g/cm}^{3}$ , often much more)
Hardness	Soft	Hard
m.p.	Low ( $< 200\degree\text{C}$ for K, Rb, Cs)	High ( $> 1000\degree\text{C}$ )
Reactivity	Very reactive	Less reactive
Reaction with water	Vigorous to explosive	Slow (Fe rusts) or none
Compound colour	White / colourless	Often coloured
Oxidation states	Always $+1$	Variable
Catalytic?	Rarely	Often
Form complex ions?	No	Often

Worked qualitative. A student is given a metal: it's hard, dense, doesn't react with cold water, forms a green compound. Likely a transition metal (e.g. Cr, Fe²⁺, or Ni).

Transition: high density / m.p., hard.
Group 1: low density, soft, melts low.
Transition: less reactive.
Transition: coloured compounds, variable oxidation.

How it’s examined

Transition metals appear most years on Paper 2 (3-4 marks: properties, comparison with Group 1) and Paper 4 (5-7 marks: identify by colour, predict reactivity). Examiner reports flag students forgetting that 'transition' refers to the GROUP location, not just any heavy metal.

Sources: Cambridge IGCSE Chemistry 0620 syllabus 2026-2028 (10.5); 0620/42 Oct/Nov 2024 — Q17 (transition metals); 0620 Examiner Reports 2022-2024. Last reviewed 2026-05-07.

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Step-by-step worked examples — Transition Elements

Step-by-step solutions to past-paper-style questions on transition elements, written exactly the way a tutor would explain them at the board.

1List four typical properties
Core• properties
Question
List four properties shared by transition elements.
Step-by-step solution
1. Step 1
  (a) High melting points and densities.
2. Step 2
  (b) Variable oxidation states.
3. Step 3
  (c) Form coloured compounds.
4. Step 4
  (d) Often act as catalysts.
Answer
High m.p., variable oxidation states, coloured compounds, catalytic activity.
2Identify by colour
Extended• Adapted from 0620/22 May/Jun 2024 Q13• colours
Question
Match each transition-metal compound to its colour: $\text{CuSO}_{4}\cdot 5\text{H}_{2}\text{O}$ , $\text{Fe}^{2+}$ (aq), $\text{Fe}^{3+}$ (aq).
Step-by-step solution
1. Step 1
  $\text{CuSO}_{4}\cdot 5\text{H}_{2}\text{O}$ : blue.
2. Step 2
  $\text{Fe}^{2+}$ (aq): pale green.
3. Step 3
  $\text{Fe}^{3+}$ (aq): yellow/orange-brown.
Answer
Cu²⁺: blue. Fe²⁺: pale green. Fe³⁺: yellow/orange.
3Catalysts in industry
Extended• catalysts
Question
Name a transition-metal catalyst used in (a) the Haber process and (b) the Contact process.
Step-by-step solution
1. Step 1
  (a) Iron in the Haber process.
2. Step 2
  (b) Vanadium(V) oxide in the Contact process.
Answer
(a) Iron. (b) $\text{V}_{2}\text{O}_{5}$ .

Key Definitions and Keywords — Transition Elements

Definitions to memorise and the exact keywords mark schemes credit for transition elements answers — sharpened from recent examiner reports for the 2026 0620 sitting.

Transition element
Examiner keyword
Element in the d-block of the Periodic Table; typically forms coloured compounds with variable oxidation states.
Variable oxidation states
Examiner keyword
Transition elements form ions of more than one charge (e.g. $\text{Fe}^{2+}$ , $\text{Fe}^{3+}$ ).

Common Mistakes and Misconceptions — Transition Elements

The traps other students keep falling into on transition elements questions — taken from recent Cambridge IGCSE 0620 examiner reports and mark schemes — and how to avoid them.

✕Saying transition metals are soft and reactive
0620/42 — recurring
Why it happens
Generalising 'metal' from Group I.
How to avoid it
Transition metals are HARD, dense and LESS reactive than Group I.
✕Always writing iron as $\text{Fe}^{2+}$
Why it happens
Defaulting to one charge.
How to avoid it
Transition metals have VARIABLE oxidation states. State which ion the question refers to.
✕Saying transition metal compounds are always white
Why it happens
Generalising from sodium chloride.
How to avoid it
Transition metal compounds are typically COLOURED — the colour depends on metal AND oxidation state.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

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Video lesson

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Transition Elements — frequently asked questions

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Transition Elements

Short Study Notes in the form of Slides

Detailed Study Notes

What you’ll learn

How it’s examined

1List four typical properties

2Identify by colour

3Catalysts in industry

Transition element

Variable oxidation states

✕Saying transition metals are soft and reactive

✕Always writing iron as Fe2+\text{Fe}^{2+}Fe2+

✕Saying transition metal compounds are always white

Practice questions

Past paper style quiz

Assess your understanding

Video lesson

Transition Elements — frequently asked questions

✕Always writing iron as $\text{Fe}^{2+}$