Transition Elements: Physical Properties
Past Paper Style Examination — Comparing Transition Elements with Group I Metals
TOPIC SUMMARY: What You Must Know
Transition elements: High melting points, high density, hard, good conductors, form coloured ions, variable oxidation states, catalytic activity.
Group I (Alkali Metals): Low melting points, low density, soft, react vigorously with water, single oxidation state (+1).
Examiner Trap: Group I metals are NOT typical metals. Their low density (Na and K float on water), softness, and explosive reactivity make them outliers.
State two physical properties that are typical of transition elements.
State two physical properties that make transition elements suitable for use as structural materials (e.g. in construction).
What is meant by the term 'variable oxidation state' as applied to transition elements? Give one example.
Explain why transition elements are good conductors of electricity. Use the term 'delocalised electrons' in your answer.
Give two uses of transition elements that rely directly on their high melting points.
How does the melting point of iron compare to the melting point of sodium? Explain why this difference exists.
How does the density of copper compare to the density of potassium? Suggest a reason for this difference.
A student claims that both iron and sodium are metals. Describe THREE physical differences between iron and sodium that show they belong to different groups in the Periodic Table.
The melting point of titanium is 1668 °C. The melting point of lithium is 181 °C. Using your knowledge of metallic bonding, explain this large difference in melting points.
Table showing melting points: Iron = 1538°C, Nickel = 1455°C, Potassium = 63°C, Lithium = 181°C. Identify which two metals are transition elements and which two are Group I alkali metals, giving one physical reason for your choice.
A civil engineer needs to choose a metal to build a bridge. Explain why iron is chosen over potassium. Give THREE reasons.
A racing car engine operates at very high temperatures. State and explain why titanium (a transition element) is preferred over caesium (a Group I metal) for engine components. [4 marks]
A student places a small piece of potassium in water in an open container. Describe what you would observe. Explain why potassium cannot be used to make water pipes.
The table shows properties of three metals: Chromium (Cr): melting point 1907°C, density 7.15 g/cm³, hardness 8.5 Mohs. Rubidium (Rb): melting point 39°C, density 1.53 g/cm³, hardness 0.3 Mohs. Vanadium (V): melting point 1910°C, density 6.11 g/cm³, hardness 7.0 Mohs. (a) Identify which metals are transition elements. (b) Explain, in terms of structure and bonding, why chromium and vanadium have much higher melting points than rubidium.
Extended Writing: Compare and contrast the physical properties of transition elements with those of Group I metals. In your answer, refer to: melting points, densities, hardness, and typical uses. [5 marks]
🔬 Quick Reference: Key Data Table
| Metal | Group | Melting Point (°C) | Density (g/cm³) | Hardness |
|---|---|---|---|---|
| Iron (Fe) | Transition | 1538 | 7.87 | Hard |
| Copper (Cu) | Transition | 1085 | 8.96 | Hard |
| Titanium (Ti) | Transition | 1668 | 4.51 | Hard |
| Chromium (Cr) | Transition | 1907 | 7.15 | Very Hard |
| Lithium (Li) | Group I | 181 | 0.53 | Soft |
| Sodium (Na) | Group I | 98 | 0.97 | Very Soft |
| Potassium (K) | Group I | 63 | 0.86 | Very Soft |
| Caesium (Cs) | Group I | 28 | 1.93 | Extremely Soft |
💡 Pattern: Transition elements have melting points above 1000°C. Group I metals all melt below 200°C. This data alone identifies the group.
🎯 Top 5 Mark-Earning Phrases for This Topic
"Electrostatic attraction between positive metal ions and delocalised electrons"
"Transition elements have much higher melting points than Group I metals"
"Potassium reacts violently/explosively with water — making it unsuitable for..."
"Iron has variable oxidation states: Fe²⁺ and Fe³⁺"
"Group I metals are soft enough to be cut with a knife; transition elements cannot"
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