Topic 8B
Groups 1 and 2
The s-block metals are the clearest example of trends down a group. These pages explain the trends in atomic radius, ionisation energy and reactivity, the reactions of the elements and their oxides, hydroxides and carbonates, the solubility and thermal stability patterns, flame colours and the tests for ions, and finish with titration calculations and measurement uncertainty.
Revision Notes
7 revision notes, in the order the specification teaches them.
Trends Down Groups 1 and 2
The trends down Group 2 and Group 1: atomic radius, ionisation energies, melting points and the increase in reactivity down the group.
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Reactions of the Group 1 and 2 Elements
The reactions of the Group 2 and Group 1 elements with oxygen, chlorine, water, steam and dilute acids, with equations, observations and redox analysis.
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Oxides, Hydroxides and Carbonates
Group 2 oxides, hydroxides and carbonates: reactions with water and acids, pH trend, and uses of Ca(OH)₂, Mg(OH)₂ and CaCO₃.
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Solubility Trends and the Sulfate Test
Group 2 solubility trends: hydroxides and sulfates, Mg(OH)₂ and BaSO₄, the acidified barium chloride test for sulfate ions and barium meals.
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Thermal Stability and Flame Colours
Thermal stability of Group 1 and 2 nitrates and carbonates, polarisation by the cation, the experiments, and flame colours explained by electron transitions.
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Tests for Ions
Tests for carbonate, hydrogencarbonate, sulfate, halide and ammonium ions, with ionic equations and the order of tests on an unknown.
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Titrations and Measurement Uncertainty
Titration calculations, concordant titres, concentrations in mol dm⁻³ and g dm⁻³, and estimating and minimising measurement uncertainty.
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Summary map
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Groups 1 and 2 Map
Edexcel International A Level Chemistry · Unit 2 · Topic 8B Trends in Groups 1 and 2
The whole section on one A4 page: trends down the groups, reactions of the metals, oxides and hydroxides, thermal stability, flame and ion tests, and titrations.
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Specification
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8.11
8.12
8.13
8.14
8.15
8.16
- a
understand reasons for trends in thermal stability of Group 1 nitrates in terms of cation size and charge
Revise - b
understand reasons for trends in thermal stability of Group 2 nitrates in terms of cation size and charge
Revise - c
understand reasons for trends in thermal stability of Group 1 carbonates in terms of cation size and charge
Revise - d
understand reasons for trends in thermal stability of Group 2 carbonates in terms of cation size and charge
Revise
8.17
8.18
- i
know experimental procedures to show: patterns in the thermal decomposition of Group 1 and 2 nitrates and carbonates Students will be expected to know tests for carbon dioxide and oxygen; and to recognise nitrogen dioxide by its colour and acidic pH.
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8.19
- i
know reactions, including ionic equations where appropriate, for identifying: carbonate ions, CO3 2-, and hydrogencarbonate ions, HCO3 - , using an aqueous acid to form carbon dioxide (and testing the gas with limewater)
Revise - ii
know reactions, including ionic equations where appropriate, for identifying: sulfate ions, SO42-, using acidified barium chloride solution
Revise - iii
know reactions, including ionic equations where appropriate, for identifying: ammonium ions, NH4 +, using sodium hydroxide solution and warming to form ammonia (and testing with litmus and HCl fumes)
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8.20
- 8.20
be able to calculate solution concentrations, in mol dm-3 and g dm-3, including simple acid-base titrations using the indicators methyl orange and phenolphthalein
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8.21
- 8.21
CORE PRACTICAL 3 Finding the concentration of a solution of hydrochloric acid.
8.22
- 8.22
understand how to minimise the sources of measurement uncertainty in volumetric analysis and estimate the overall uncertainty in the calculated result
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8.27
- ii
understand the following reactions: precipitation reactions of the aqueous anions Cl-, Br- and I- with aqueous silver nitrate solution and nitric acid, and the solubility of the precipitates in aqueous ammonia solution
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