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This lesson covers the transition metals as required by AQA GCSE Chemistry specification (5.1.2). The transition metals are the large block of metallic elements found in the centre of the periodic table, between Group 2 and Group 3. They include many familiar metals such as iron, copper, gold, and silver. Compared to the alkali metals (Group 1), transition metals are harder, stronger, denser, and much less reactive.
The transition metals occupy the central block of the periodic table, spanning Periods 4 to 7 and sitting between Group 2 (alkaline earth metals) and Group 3. Common examples include:
| Element | Symbol | Atomic Number | Common Uses |
|---|---|---|---|
| Titanium | Ti | 22 | Aircraft, joint replacements, spectacle frames |
| Chromium | Cr | 24 | Stainless steel, chrome plating |
| Manganese | Mn | 25 | Steel production, batteries |
| Iron | Fe | 26 | Steel, construction, vehicles |
| Cobalt | Co | 27 | Magnets, batteries, alloys |
| Nickel | Ni | 28 | Coins, stainless steel, batteries |
| Copper | Cu | 29 | Electrical wiring, plumbing, coins |
| Zinc | Zn | 30 | Galvanising, batteries, alloys (brass) |
| Silver | Ag | 47 | Jewellery, electronics, photography |
| Gold | Au | 79 | Jewellery, electronics, dental work |
| Platinum | Pt | 78 | Catalytic converters, jewellery |
Exam Tip: At GCSE, you do not need to know the detailed electronic configurations of transition metals. However, you do need to know their general properties and how they compare to Group 1 metals. Focus on the key differences: transition metals are harder, stronger, denser, and less reactive.
Transition metals have typical metallic properties but are generally much harder and stronger than Group 1 metals.
| Property | Transition Metals | Comparison with Group 1 |
|---|---|---|
| Hardness | Hard and strong | Group 1 metals are very soft (can be cut with a knife) |
| Density | High density | Group 1 metals have low density (Li, Na, K float on water) |
| Melting point | High melting points (typically > 1000 degrees C) | Group 1 metals have low melting points (Na melts at 98 degrees C) |
| Strength | Strong — can be used in construction | Group 1 metals are too soft and reactive for structural use |
| Conductivity | Good conductors of heat and electricity | Both groups conduct well |
| Malleability | Malleable and ductile | Group 1 metals are malleable but too reactive to be useful |
| Metal | Melting Point (degrees C) |
|---|---|
| Sodium (Group 1) | 98 |
| Potassium (Group 1) | 63 |
| Iron (Transition) | 1538 |
| Copper (Transition) | 1085 |
| Gold (Transition) | 1064 |
| Tungsten (Transition) | 3422 |
Transition metals have several distinctive chemical properties that set them apart from Group 1 metals:
Unlike Group 1 metals (which always form +1 ions), transition metals can form ions with different charges (oxidation states). This allows them to form more than one type of compound.
| Metal | Common Ions | Example Compounds |
|---|---|---|
| Iron | Fe2+ (iron(II)), Fe3+ (iron(III)) | FeCl2 (iron(II) chloride), FeCl3 (iron(III) chloride) |
| Copper | Cu+ (copper(I)), Cu2+ (copper(II)) | Cu2O (copper(I) oxide), CuO (copper(II) oxide) |
| Manganese | Mn2+, Mn4+, Mn7+ | MnO2 (manganese(IV) oxide), KMnO4 (potassium manganate(VII)) |
| Chromium | Cr2+, Cr3+, Cr6+ | Cr2O3 (chromium(III) oxide), K2Cr2O7 (potassium dichromate(VI)) |
The Roman numeral in the name of the compound tells you the charge on the metal ion.
Exam Tip: When a transition metal compound has a Roman numeral in its name, this tells you the oxidation state (charge) of the metal ion. Iron(II) chloride contains Fe2+ ions, while iron(III) chloride contains Fe3+ ions. This naming convention is essential for writing correct formulae.
Transition metals form coloured compounds, unlike Group 1 metals (which form white or colourless compounds).
| Metal Ion | Colour |
|---|---|
| Fe2+ (iron(II)) | Pale green |
| Fe3+ (iron(III)) | Orange-brown / rust |
| Cu2+ (copper(II)) | Blue |
| Mn2+ (manganese(II)) | Pale pink |
| Cr3+ (chromium(III)) | Green |
| Co2+ (cobalt(II)) | Pink |
| Ni2+ (nickel(II)) | Green |
These colours are why transition metal compounds are widely used as pigments in paints, ceramics, and glass.
Many transition metals and their compounds are excellent catalysts — substances that speed up chemical reactions without being used up.
| Catalyst | Reaction |
|---|---|
| Iron | Haber process (making ammonia: N2 + 3H2 → 2NH3) |
| Manganese(IV) oxide (MnO2) | Decomposition of hydrogen peroxide (2H2O2 → 2H2O + O2) |
| Nickel | Hydrogenation of vegetable oils (making margarine) |
| Platinum / Palladium / Rhodium | Catalytic converters in cars (reducing exhaust emissions) |
| Vanadium(V) oxide (V2O5) | Contact process (making sulfuric acid) |
Exam Tip: You need to know that iron is the catalyst in the Haber process. This is one of the most commonly tested facts about transition metals. Also remember that transition metals are used as catalysts because they can change oxidation state, allowing them to facilitate electron transfer in reactions.
graph TD
A["Metallic Elements"] --> B["Group 1 (Alkali Metals)"]
A --> C["Transition Metals"]
B --> D["Soft, low density"]
B --> E["Low melting points"]
B --> F["Very reactive"]
B --> G["Always form +1 ions"]
B --> H["White/colourless compounds"]
C --> I["Hard, high density"]
C --> J["High melting points"]
C --> K["Less reactive"]
C --> L["Variable oxidation states"]
C --> M["Coloured compounds"]
C --> N["Often good catalysts"]
style A fill:#2c3e50,color:#fff
style B fill:#e74c3c,color:#fff
style C fill:#3498db,color:#fff
Transition metals are generally much less reactive than Group 1 metals. Many transition metals are found naturally in their elemental form (e.g. gold, platinum) because they are so unreactive.
| Reactivity | Group 1 Metals | Transition Metals |
|---|---|---|
| Reaction with water | Vigorous (e.g. sodium fizzes, potassium catches fire) | Most do not react with water at room temperature (iron rusts slowly over time) |
| Reaction with oxygen | React very quickly (tarnish immediately) | React slowly or not at all (gold does not tarnish) |
| Reaction with dilute acid | Very vigorous (dangerous) | Moderate or slow (e.g. iron reacts slowly with dilute HCl) |
| Storage | Must be stored under oil | Can be stored in air without special precautions |
Transition metals have more protons in their nucleus and their outer electrons are more strongly held (though the detailed explanation involves d-electron shielding, which is beyond GCSE). The key point is that they do not lose their outer electrons as easily as Group 1 metals.
Transition metals are widely used in everyday life because of their strength, durability, conductivity, and low reactivity.
| Use | Metal | Property Exploited |
|---|---|---|
| Electrical wiring | Copper | Excellent electrical conductor, ductile |
| Construction (steel) | Iron (as steel) | Strong, hard, high melting point |
| Jewellery | Gold, Silver, Platinum | Unreactive (does not tarnish), attractive appearance |
| Coins | Copper, Nickel | Hard-wearing, unreactive, distinctive appearance |
| Catalytic converters | Platinum, Palladium, Rhodium | Catalytic properties |
| Aircraft | Titanium | Strong, low density, corrosion-resistant |
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