Doc Brown's Chemistry AQA GCSE Science-CHEMISTRY 1 Revision Notes

Unit C1.1 The fundamental ideas in chemistry Study Notes

CHEMISTRY UNIT 1 Chemistry 1 for GCSE Science or GCSE Chemistry

PLEASE NOTE NEW revision summaries for the NEW AQA GCSE Chemistry and NEW AQA GCSE Combined Science Trilogy Chemistry courses: Revision for Paper 1 (Topics 1-5 and 8-12) and  Paper 2 (Topics 6-10 and 13-17) STARTING with Y10 in Sept. 2016 onwards, first exams in 2018

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 C1.1 The fundamental ideas in chemistry

AQA GCSE Science CHEMISTRY Unit C1.1.1 Atoms

(c) doc b

  • a) All substances are made of atoms.

    • A substance that is made of only one sort of atom is called an element.

    • There are about 100 different elements.

    • Elements are shown in the periodic table.

    • You should know where metals and non-metals are in the periodic table.

    • The groups contain elements with similar properties.

  • b) Atoms of each element are represented by a chemical symbol,

    • eg O represents an atom of oxygen, and Na represents an atom of sodium and others.

      • You do not need to know the chemical symbols for elements if they are not named in the specification-syllabus.

  • c) Atoms have a small central nucleus, which is made up of protons and neutrons and around which there are electrons which move in specific energy levels (a sort of orbit, often called a shell) in the majority of the space of an atom.

  • d) Know their relative electrical charges i.e. proton is +1 and neutron 0 and the electron 1

  • e) In a neutral atom, the number of electrons is equal to the number of protons in the nucleus.

    • Therefore atoms have no overall electrical charge ie overall neutral (+ balances -).

      • Removing electrons from atoms makes positive ions.

      • Adding electrons to atoms makes negative ions.

  • f) All atoms of a particular element have the same number of protons.

    • Atoms of different elements have different numbers of protons.

    • Elements consist of one type of atom only.

  • g) The number of protons in an atom of an element is its atomic number.

    • The sum of the protons and neutrons in an atom is its mass number.

  • h) (c) doc bElectrons occupy particular energy levels.

    • Each electron in an atom is at a particular energy level (in a particular shell).

    • The electrons in an atom occupy the lowest available energy levels (innermost available shells).

    • You can use the term energy level or shell for where an electron is.

    • You should be able to represent the electronic structure of the first 20 elements of the periodic table in the following forms e.g sodium 2,8,1 or as in the diagram on the right.

  • Revision notes:

AQA GCSE Science CHEMISTRY Unit C1.1.2 The periodic table

AQA GCSE Science CHEMISTRY Unit C1.1.3 Chemical reactions

(c) doc b

  • a) When elements react, their atoms join with other atoms to form compounds.

    • This involves giving, taking or sharing electrons to form ions or molecules.

    • Compounds formed from metals and non-metals consist of ions (electrically charged particles) - hence called ionic compounds.

    • You do not need to know further details of the types of bonding here.

    • You should know that metals lose electrons to form positive ions, whereas non-metals gain electrons to form negative ions - but . only in terms of single electron transfers.

      • e.g. metallic sodium forms a sodium ion by electron loss: Na ==> Na+ + e- 

      • and non-metal chlorine atoms form a chloride ion by electron gain: Cl + e- ==> Cl- 

    • Compounds formed from non-metals consist of molecules. In molecules the atoms are held together by covalent bonds, hence know as covalent compounds.

    • Revision Notes:

  • b) Chemical reactions can be represented by word equations or by symbol equations.

  • c) No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.

  • Hopefully your school practical work included the following (which should also be revised, helps in understanding 'how science works' and context examination questions):

    • modelling of atoms (using physical models or computer simulations) to illustrate chemical reactions at the atomic level,

    • observing/measuring? precipitation reactions, such as lead nitrate with potassium iodide, to show conservation of mass.

AQA GCSE Sciences - Revision Notes

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