AS Chemistry₇₄₀₄

AS and A-level Chemistry Specification Specifications for first teaching in 2015

12 Jan 2015

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3.2 Inorganic chemistry

3.2.1 Periodicity

The Periodic Table provides chemists with a structured organisation of the known chemical elements from which they can make sense of their physical and chemical properties. The historical development of the Periodic Table and models of atomic structure provide good examples of how scientific ideas and explanations develop over time.

3.2.1.1 Classification

Content	Opportunities for skills development
An element is classified as s, p, d or f block according to its position in the Periodic Table, which is determined by its proton number.

3.2.1.2 Physical properties of Period 3 elements

Content	Opportunities for skills development
The trends in atomic radius, first ionisation energy and melting point of the elements Na–Ar The reasons for these trends in terms of the structure of and bonding in the elements. Students should be able to: explain the trends in atomic radius and first ionisation energy explain the melting point of the elements in terms of their structure and bonding.

Content

Opportunities for skills development

The trends in atomic radius, first ionisation energy and melting point of the elements Na–Ar

The reasons for these trends in terms of the structure of and bonding in the elements.

Students should be able to:

explain the trends in atomic radius and first ionisation energy
explain the melting point of the elements in terms of their structure and bonding.

3.2.2 Group 2, the alkaline earth metals

The elements in Group 2 are called the alkaline earth metals. The trends in the solubilities of the hydroxides and the sulfates of these elements are linked to their use. Barium sulfate, magnesium hydroxide and magnesium sulfate have applications in medicines whilst calcium hydroxide is used in agriculture to change soil pH, which is essential for good crop production and maintaining the food supply.

Content	Opportunities for skills development
The trends in atomic radius, first ionisation energy and melting point of the elements Mg–Ba Students should be able to: explain the trends in atomic radius and first ionisation energy explain the melting point of the elements in terms of their structure and bonding. The reactions of the elements Mg–Ba with water. The use of magnesium in the extraction of titanium from TiCl₄ The relative solubilities of the hydroxides of the elements Mg–Ba in water. Mg(OH)₂ is sparingly soluble. The use of Mg(OH)₂ in medicine and of Ca(OH)₂ in agriculture. The use of CaO or CaCO₃ to remove SO₂ from flue gases. The relative solubilities of the sulfates of the elements Mg–Ba in water. BaSO₄ is insoluble. The use of acidified BaCl₂ solution to test for sulfate ions. The use of BaSO₄ in medicine. Students should be able to: explain why BaCl₂ solution is used to test for sulfate ions and why it is acidified.	AT c and k PS 2.2 Students could test the reactions of Mg–Ba with water and Mg with steam and record their results. AT d and k PS 2.2 Students could test the solubility of Group 2 hydroxides by mixing solutions of soluble Group 2 salts with sodium hydroxide and record their results. Students could test the solubility of Group 2 sulfates by mixing solutions of soluble Group 2 salts with sulfuric acid and record their results. Students could test for sulfate ions using acidified barium chloride and record their results. Research opportunity Students could investigate the use of BaSO₄ in medicine.

Content

Opportunities for skills development

The trends in atomic radius, first ionisation energy and melting point of the elements Mg–Ba

Students should be able to:

explain the trends in atomic radius and first ionisation energy
explain the melting point of the elements in terms of their structure and bonding.

The reactions of the elements Mg–Ba with water.

The use of magnesium in the extraction of titanium from TiCl₄

The relative solubilities of the hydroxides of the elements Mg–Ba in water.

Mg(OH)₂ is sparingly soluble.

The use of Mg(OH)₂ in medicine and of Ca(OH)₂ in agriculture.

The use of CaO or CaCO₃ to remove SO₂ from flue gases.

The relative solubilities of the sulfates of the elements Mg–Ba in water.

BaSO₄ is insoluble.

The use of acidified BaCl₂ solution to test for sulfate ions.

The use of BaSO₄ in medicine.

Students should be able to:

explain why BaCl₂ solution is used to test for sulfate ions and why it is acidified.

AT c and k

PS 2.2

Students could test the reactions of Mg–Ba with water and Mg with steam and record their results.

AT d and k

PS 2.2

Students could test the solubility of Group 2 hydroxides by mixing solutions of soluble Group 2 salts with sodium hydroxide and record their results.

Students could test the solubility of Group 2 sulfates by mixing solutions of soluble Group 2 salts with sulfuric acid and record their results.

Students could test for sulfate ions using acidified barium chloride and record their results.

Research opportunity

Students could investigate the use of BaSO₄ in medicine.

3.2.3 Group 7(17), the halogens

The halogens in Group 7 are very reactive non-metals. Trends in their physical properties are examined and explained. Fluorine is too dangerous to be used in a school laboratory but the reactions of chlorine are studied. Challenges in studying the properties of elements in this group include explaining the trends in ability of the halogens to behave as oxidising agents and the halide ions to behave as reducing agents.

3.2.3.1 Trends in properties

Content	Opportunities for skills development
The trends in electronegativity and boiling point of the halogens. Students should be able to: explain the trend in electronegativity explain the trend in the boiling point of the elements in terms of their structure and bonding. The trend in oxidising ability of the halogens down the group, including displacement reactions of halide ions in aqueous solution. The trend in reducing ability of the halide ions, including the reactions of solid sodium halides with concentrated sulfuric acid. The use of acidified silver nitrate solution to identify and distinguish between halide ions. The trend in solubility of the silver halides in ammonia. Students should be able to explain why: silver nitrate solution is used to identify halide ions the silver nitrate solution is acidified ammonia solution is added.	AT d and k PS 2.2 Students could carry out test-tube reactions of solutions of the halogens (Cl₂ , Br₂ , I₂ ) with solutions containing their halide ions (eg KCl, KBr, KI). Students could record observations from reactions of NaCl, NaBr and NaI with concentrated sulfuric acid. Students could carry out tests for halide ions using acidified silver nitrate, including the use of ammonia to distinguish the silver halides formed.

Content

Opportunities for skills development

The trends in electronegativity and boiling point of the halogens.

Students should be able to:

explain the trend in electronegativity
explain the trend in the boiling point of the elements in terms of their structure and bonding.

The trend in oxidising ability of the halogens down the group, including displacement reactions of halide ions in aqueous solution.

The trend in reducing ability of the halide ions, including the reactions of solid sodium halides with concentrated sulfuric acid.

The use of acidified silver nitrate solution to identify and distinguish between halide ions.

The trend in solubility of the silver halides in ammonia.

Students should be able to explain why:

silver nitrate solution is used to identify halide ions
the silver nitrate solution is acidified
ammonia solution is added.

AT d and k

PS 2.2

Students could carry out test-tube reactions of solutions of the halogens (Cl₂ , Br₂ , I₂ ) with solutions containing their halide ions (eg KCl, KBr, KI).

Students could record observations from reactions of NaCl, NaBr and NaI with concentrated sulfuric acid.

Students could carry out tests for halide ions using acidified silver nitrate, including the use of ammonia to distinguish the silver halides formed.

3.2.3.2 Uses of chlorine and chlorate(I)

Content	Opportunities for skills development
The reaction of chlorine with water to form chloride ions and chlorate(I) ions. The reaction of chlorine with water to form chloride ions and oxygen. Appreciate that society assesses the advantages and disadvantages when deciding if chemicals should be added to water supplies. The use of chlorine in water treatment. Appreciate that the benefits to health of water treatment by chlorine outweigh its toxic effects. The reaction of chlorine with cold, dilute, aqueous NaOH and uses of the solution formed.	Research opportunity Students could investigate the treatment of drinking water with chlorine. Students could investigate the addition of sodium fluoride to water supplies.
Required practical 4 Carry out simple test-tube reactions to identify: cations – Group 2, NH₄ ⁺ anions – Group 7 (halide ions), OH^– , CO₃ ^2– , SO₄ ^2–

Content

Opportunities for skills development

The reaction of chlorine with water to form chloride ions and chlorate(I) ions.

The reaction of chlorine with water to form chloride ions and oxygen.

Appreciate that society assesses the advantages and disadvantages when deciding if chemicals should be added to water supplies.

The use of chlorine in water treatment.

Appreciate that the benefits to health of water treatment by chlorine outweigh its toxic effects.

The reaction of chlorine with cold, dilute, aqueous NaOH and uses of the solution formed.

Research opportunity

Students could investigate the treatment of drinking water with chlorine.

Students could investigate the addition of sodium fluoride to water supplies.

Required practical 4 Carry out simple test-tube reactions to identify:

cations – Group 2, NH₄ ⁺
anions – Group 7 (halide ions), OH^– , CO₃ ^2– , SO₄ ^2–

3.1 Physical chemistry

3.3 Organic chemistry