Doc Brown's Chemistry AQA GCSE Science-CHEMISTRY 2 Revision Notes

Chemistry Unit C2.1 Structure and bonding Study Notes

CHEMISTRY UNIT 2 Chemistry 2 for GCSE Additional Science or GCSE Chemistry

REVISION NOTES GUIDE SUMMARY: What do you need to know for the examinations? What do you need to able to do in the exams? In AQA GCSE Science A examinations HT means for higher tier students only. Sorry, but I don't have much time to answer questions, but if you see any apparent errors or wish to comment, please email me. All my notes, learning objectives, comments for exam revision are based on the official AQA GCSE Science A Key Stage 4 syllabus specification.

  • Throughout this unit you will be expected to write word equations for reactions specified.

  • Higher tier (HT) candidates will also be expected to write and balance symbol equations for reactions specified throughout the unit.

AQA GCSE Science CHEMISTRY Unit C2.1 Structure and bonding

  • Simple particle theory is developed in this unit to include atomic structure and bonding.

  • You should understand that the arrangement of electrons in atoms can be used to explain what happens when elements react and how atoms join together to form different types of substances.

  • You should be able to use your skills, knowledge and understanding to:

    • write formulae for ionic compounds from given symbols and ionic charges.

    • represent the electronic structure of the ions in sodium chloride, magnesium oxide and calcium chloride in the following form:

      • eg for the sodium ion (Na+)

      • and for the chloride ion, the 'blob' electron represents the one gained to form a chloride ion [2.8.8]- from a chlorine atom [2.8.7].

      • Hence represent ionic compounds such as magnesium oxide Mg2+O2-

    • represent the covalent bonds in molecules such as water H2O, ammonia NH3, hydrogen H2, hydrogen chloride HCl, methane CH4 and oxygen O2, and in giant structures such as diamond and silicon dioxide, in the following forms:

    • HT only represent the bonding in metals in the following form:

AQA GCSE Science CHEMISTRY Unit C2.1.1 Structure and bonding

  • a) Know that compounds are substances in which atoms of two or more elements are chemically combined.

  • b) Know that chemical bonding involves either transferring or sharing electrons in the highest occupied energy levels (shells) of atoms in order to achieve the electronic structure of a noble gas.

  • c) Know that when atoms form chemical bonds by transferring electrons, they form ions.

    • Atoms that lose electrons become positively charged ions.

    • Atoms that gain electrons become negatively charged ions.

    • Ions have the electronic structure of a noble gas (Group 0).

    • You should be able to relate the charge on simple ions to the group number of the element in the periodic table.

  • d) Know that the elements in Group 1 of the periodic table, the alkali metals, all react with non-metal elements to form ionic compounds in which the metal ion has a single positive charge.

    • Your knowledge of the chemical properties of alkali metals is limited to their reactions with non-metal elements.

  • e) Know that the elements in Group 7 of the periodic table, the halogens, all react with the alkali metals to form ionic compounds in which the halide ions have a single negative charge.

    • Knowledge of the chemical properties of the halogens is limited to reactions with alkali metals.

  • f) Know that an ionic compound is a giant structure of ions.

    • Know that ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions.

    • Understand that these forces act in all directions in the lattice and this is called ionic bonding.

    • You should be familiar with the structure of sodium chloride but do not need to know the structures of other ionic compounds.

  • g) Know that when atoms share pairs of electrons, they form covalent bonds.

    • Know that these covalent bonds between atoms are strong.

    • Know that some covalently bonded substances consist of simple molecules such as H2, Cl2, O2, HCl, H2O, NH3 and CH4

    • Know that others have giant covalent structures (macromolecules), such as diamond and silicon dioxide.

    • You should know the bonding in the examples in the specification for this unit, and should be able to recognise simple molecules and giant structures from diagrams that show their bonding.

  • h) Know that metals consist of giant structures of atoms arranged in a regular pattern.

  • i) HT only: The electrons in the highest occupied energy levels (outer shell) of metal atoms are delocalised and so free to move through the whole structure.


OCR GCSE 21st Century Science A CHEMISTRY  *  OCR GCSE Gateway Science B CHEMISTRY

WJEC GCSE Science-CHEMISTRY  *  Northern Ireland CCEA GCSE Science-CHEMISTRY

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