What you'll learn
Transition metals occupy the central block of the periodic table and display distinctive physical and chemical properties. This topic focuses on their position in the periodic table, characteristic properties, and practical applications. You'll need to compare transition metals with Group 1 metals and explain why transition metals are so useful in industry and everyday life.
Key terms and definitions
Transition metals — Elements found in the central block of the periodic table between Groups 2 and 3, characterized by their ability to form ions with different charges and coloured compounds.
Catalyst — A substance that increases the rate of a chemical reaction without being used up or permanently changed in the reaction.
Thermal decomposition — A chemical reaction where one substance breaks down into two or more substances when heated.
Ion — An atom or group of atoms that has lost or gained electrons, giving it a positive or negative charge.
Compound — A substance formed from two or more elements chemically bonded together in fixed proportions.
Reactivity series — A list of metals arranged in order of their reactivity, with the most reactive at the top.
Core concepts
Location and identification of transition metals
The transition metals are located in the central block of the periodic table, between Group 2 and Group 3. At GCSE level, you need to focus on the elements in the block that includes:
- Iron (Fe)
- Copper (Cu)
- Chromium (Cr)
- Manganese (Mn)
- Nickel (Ni)
- Zinc (Zn) — often included with transition metals at GCSE
These elements are all metals and share similar properties. On the periodic table, they occupy the section between calcium/scandium and gallium, spanning Groups 3-12 in modern numbering (though GCSE typically refers to them as "the transition metals" rather than by group number).
Physical properties of transition metals
Transition metals have characteristic physical properties that make them extremely useful:
High melting points and boiling points
- Most transition metals have much higher melting points than Group 1 metals
- Iron melts at 1538°C compared to sodium at 98°C
- These high melting points make them suitable for structural applications and high-temperature uses
High density
- Transition metals are typically dense metals
- Iron has a density of 7.87 g/cm³
- Copper has a density of 8.96 g/cm³
- Compare this to sodium (Group 1) with density 0.97 g/cm³
Strength and hardness
- Transition metals are strong and hard
- They can be bent and shaped without breaking (malleable)
- They can be drawn into wires (ductile)
- Iron and its alloys (steels) are used in construction because of their strength
Good conductors
- Excellent conductors of electricity
- Copper is widely used in electrical wiring
- Also good conductors of heat
Chemical properties of transition metals
Transition metals display distinctive chemical properties that distinguish them from other metals:
Formation of ions with different charges
Unlike Group 1 metals (which always form +1 ions), transition metals can form ions with different charges:
- Iron forms Fe²⁺ and Fe³⁺ ions
- Copper forms Cu⁺ and Cu²⁺ ions (Cu²⁺ is more common)
- Chromium forms Cr³⁺ and Cr⁶⁺ ions
This ability to form multiple ions with different charges is a key characteristic property at GCSE level.
Formation of coloured compounds
Transition metal compounds are typically coloured, unlike Group 1 metal compounds which are usually white:
- Copper(II) compounds are often blue or green
- Iron(II) compounds are often pale green
- Iron(III) compounds are often orange/brown
- Chromium(III) compounds are often green
- Manganese compounds can be pink or purple
The colour depends on both the metal and the other elements it's combined with. For example:
- Copper(II) sulfate solution is blue
- Copper(II) carbonate is green
- Iron(III) oxide is red-brown (rust)
Catalytic activity
Many transition metals and their compounds act as catalysts:
- Iron is used as a catalyst in the Haber process (making ammonia)
- Nickel is used as a catalyst in hydrogenation reactions (converting oils to fats)
- Platinum and rhodium are used in catalytic converters in car exhausts
- Manganese(IV) oxide catalyzes the decomposition of hydrogen peroxide
The ability to act as catalysts makes transition metals extremely valuable in industrial processes.
Comparison with Group 1 metals
A common exam question requires you to compare transition metals with Group 1 metals (lithium, sodium, potassium, etc.). Here are the key differences:
Melting and boiling points
- Group 1: Low melting/boiling points (sodium melts at 98°C)
- Transition metals: High melting/boiling points (iron melts at 1538°C)
Density
- Group 1: Low density (sodium is 0.97 g/cm³, floats on water)
- Transition metals: High density (copper is 8.96 g/cm³)
Strength
- Group 1: Soft, can be cut with a knife
- Transition metals: Hard and strong
Reactivity with water and oxygen
- Group 1: Very reactive, react vigorously with water and oxygen, must be stored under oil
- Transition metals: Much less reactive, iron rusts slowly in air, copper doesn't react with water
Ion formation
- Group 1: Form ions with only one charge (+1)
- Transition metals: Form ions with different charges (e.g., Fe²⁺ and Fe³⁺)
Compounds formed
- Group 1: Compounds are white or colorless
- Transition metals: Compounds are colored
Catalytic properties
- Group 1: Not used as catalysts
- Transition metals: Many are excellent catalysts
Thermal decomposition of transition metal carbonates
Transition metal carbonates undergo thermal decomposition when heated. This is a chemical reaction you need to understand:
General equation: Metal carbonate → Metal oxide + Carbon dioxide
Specific examples:
Copper(II) carbonate → Copper(II) oxide + Carbon dioxide
CuCO₃(s) → CuO(s) + CO₂(g)
Zinc carbonate → Zinc oxide + Carbon dioxide
ZnCO₃(s) → ZnO(s) + CO₂(g)
Observable changes:
- Copper carbonate is green; copper oxide is black
- Zinc carbonate is white; zinc oxide is yellow when hot, white when cold
- The color change provides evidence that a chemical reaction has occurred
- Carbon dioxide can be detected using limewater (turns cloudy/milky)
This reaction can be used to distinguish transition metal carbonates from Group 1 carbonates. Lithium carbonate decomposes on heating, but sodium and potassium carbonates are very stable and do not decompose at the temperatures available in a school laboratory.
Uses of transition metals
Understanding the practical applications of transition metals helps explain why they're so important:
Iron and steel
- Construction (buildings, bridges)
- Vehicles and machinery
- Tools
- Steel is iron alloyed with carbon and other elements to improve properties
Copper
- Electrical wiring (excellent conductor)
- Water pipes (doesn't react with water, can be bent easily)
- Cooking pans (good heat conductor)
Chromium
- Electroplating (protects objects from corrosion and makes them shiny)
- Stainless steel manufacture
Nickel
- Coins (mixed with copper)
- Stainless steel manufacture
- Rechargeable batteries
Zinc
- Galvanizing (coating iron to prevent rusting)
- Brass manufacture (alloy with copper)
- Batteries
Worked examples
Example 1: Comparing transition metals with Group 1 metals
Question: Sodium is a Group 1 metal. Iron is a transition metal. Compare the properties of sodium and iron. [4 marks]
Mark scheme answer:
- Iron has a higher melting point than sodium (1 mark)
- Iron is stronger/harder than sodium OR sodium is soft (1 mark)
- Iron is less reactive than sodium OR sodium reacts more vigorously with water/oxygen (1 mark)
- Iron forms ions with different charges (Fe²⁺ and Fe³⁺) whereas sodium only forms Na⁺ ions (1 mark)
Alternative acceptable answers for marks:
- Iron has higher density than sodium
- Iron compounds are colored whereas sodium compounds are white
- Iron/iron compounds can act as catalysts but sodium cannot
Example 2: Thermal decomposition
Question: A student heats some green copper carbonate powder in a test tube. The powder turns black and a gas is produced.
(a) Name the black solid formed. [1 mark] (b) Describe a test to identify the gas produced. [2 marks] (c) Write a word equation for this reaction. [2 marks]
Mark scheme answer:
(a) Copper(II) oxide OR copper oxide [1 mark]
(b) Bubble the gas through limewater [1 mark] The limewater turns cloudy/milky [1 mark] (Note: Both parts needed for full marks)
(c) Copper carbonate → Copper oxide + Carbon dioxide [2 marks] (Award 1 mark if only one product is incorrect)
Example 3: Catalysts
Question: Transition metals are often used as catalysts.
(a) What is a catalyst? [2 marks] (b) Give one example of a transition metal used as a catalyst and state what process it catalyzes. [2 marks]
Mark scheme answer:
(a) A substance that speeds up/increases the rate of a chemical reaction [1 mark] Without being used up OR without being permanently changed [1 mark] (Both points needed for full marks)
(b) Any one from:
- Iron used in the Haber process (making ammonia)
- Nickel used in hydrogenation (making margarine)
- Platinum/rhodium used in catalytic converters
- Manganese(IV) oxide used to decompose hydrogen peroxide [1 mark for correct metal, 1 mark for correct process]
Common mistakes and how to avoid them
Confusing the location of transition metals. Don't say they're in Groups 1-3 or on the left side of the periodic table. They're in the central block between Groups 2 and 3. Learn that iron and copper are typical examples.
Stating that ALL transition metals form multiple ions. At GCSE, focus on the fact that transition metals CAN form ions with different charges (like Fe²⁺ and Fe³⁺), but you don't need to memorize all possibilities. Stick to iron and copper as examples.
Writing incomplete catalyst definitions. A complete definition must include BOTH that catalysts speed up reactions AND that they're not used up. Missing either part loses marks.
Forgetting color changes in thermal decomposition. When describing the decomposition of copper carbonate, specify that green changes to black. The color change is evidence of a chemical reaction.
Mixing up properties of Group 1 and transition metals. Group 1 metals are soft, low density, low melting point, and very reactive. Transition metals are hard, high density, high melting point, and less reactive. Don't confuse them.
Not testing for carbon dioxide properly. When asked to identify CO₂, you must say "bubble through limewater" AND "turns cloudy/milky." Just saying "use limewater" isn't enough for full marks.
Exam technique for "Transition metals"
"Compare" questions require differences for both substances. If asked to compare sodium and iron, make sure each point clearly contrasts both metals. Write: "Iron has a higher melting point than sodium" not just "Iron has a high melting point."
Extended response questions on properties. If a question is worth 4-6 marks, you need 4-6 distinct points. Cover physical properties (melting point, density, strength), chemical properties (reactivity, ion charges, colored compounds), and uses or catalytic activity.
Command word "Describe a test" means method AND result. Always give the procedure (e.g., "add limewater") and the positive result (e.g., "turns cloudy"). Both are needed.
Equations can be word or symbol equations at GCSE. For thermal decomposition of carbonates, word equations are acceptable. Make sure you include all three substances: metal carbonate → metal oxide + carbon dioxide.
Quick revision summary
Transition metals are elements in the central block of the periodic table, including iron, copper, and chromium. They have high melting points, high density, and are strong and hard compared to Group 1 metals. Transition metals form ions with different charges (Fe²⁺ and Fe³⁺), produce colored compounds, and act as catalysts in many industrial processes. Their carbonates undergo thermal decomposition when heated to produce the metal oxide and carbon dioxide. These properties make transition metals extremely useful in construction, electrical applications, and chemical manufacturing.