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Group 2, the alkaline earth metals
This topic links Group 2 reactivity and solubility trends to practical applications.
7
Objectives
35
Flashcards
35
Questions
90 min
Study time
AQAA LevelChemistryInorganic chemistry
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Syllabus checklist
What you need to know
7 objective pages available
Group 2 trends and reactions4 objectives
- Explain trends in atomic radius and first ionisation energy down Group 2.
- Describe reactions of Group 2 metals with oxygen, water and acids.
- Explain the trend in reactivity down Group 2.
- Explain trends in solubility of Group 2 hydroxides and sulfates.
Group 2 applications3 objectives
- Explain why barium sulfate can be used in medicine despite barium compounds often being toxic.
- Explain uses of magnesium hydroxide and calcium carbonate in neutralising acidity.
- Link Group 2 solubility trends to applications.
Key terms
atomic radiusfirst ionisation energyGroup 2 metalsreactivityreactivity trendionisation energyHydroxide solubility trendSulfate solubility trendbarium sulfatetoxicitymagnesium hydroxidecalcium carbonate
Exam tips
- Understanding Atomic Radius Trends: Explain clearly by remember that atomic radius increases down Group 2 due to additional electron shells. Link the point to Group 2 trends and reactions, then state the evidence, calculation, mechanism, observation, or conclusion required by the question.
- Understanding Group 2 Metal Reactions: Explain clearly by memorize the general reaction patterns of Group 2 metals with oxygen, water, and acids. For example, when magnesium reacts with hydrochloric acid, it produces magnesium chloride and hydrogen gas. Link the point to Group 2 trends and reactions, then state the evidence, calculation, mechanism, observation, or conclusion required by the question.
Common mistakes
- Atomic radius trend misinterpreted: Explain that as you move down Group 2 the principal quantum number increases, adding a new shell which outweighs the increased nuclear charge, so the outer electrons are further from the nucleus and the atomic radius increases. Use the rule that the effective nuclear charge felt by the outermost electrons decreases slightly because of shielding, leading to a larger radius.
- Misunderstanding Group 2 Metal Reactivity: To clarify, remember that Group 2 metals react with oxygen to form metal oxides, with water to produce hydroxides and hydrogen gas, and with acids to yield salts and hydrogen gas. For example, the reaction of magnesium with water can be represented as: 1. **Formula**: Mg + 2H2O → Mg(OH)2 + H2 2. **Substitution**: Here, magnesium reacts with water to form magnesium hydroxide and hydrogen gas. 3. **Working**: The magnesium displaces hydrogen from water, resulting in the formation of magnesium hydroxide. 4. **Answer**: The products are magnesium hydroxide (Mg(OH)2) and hydrogen gas (H2). 5. **Units/Conclusion**: This shows that Group 2 metals react with water to produce hydroxides, which is a key characteristic of their reactivity.
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