Key term
AQA GCSE Combined Science Chemistry 8464
Atomic Structure and the Periodic Table
Topic overviewAtoms, elements and compoundsWord equations, symbols and balanced equationsMixturesFrom the plum pudding model to the nuclear modelBohr, Chadwick and the modern model of the atomRelative electrical charges of subatomic particlesSize and mass of atomsRelative atomic mass and electronic structureThe periodic tableDevelopment of the periodic tableMetals and non-metalsGroup 0Group 1Group 7
Bonding, Structure, and the Properties of Matter
Topic overviewChemical bonds, including metallic bondingIonic bondingIonic compoundsCovalent bonding and how it is representedThe three states of matter and changes of statePredicting state, state symbols, and the limits of the particle modelProperties of ionic compoundsProperties of small moleculesPolymers and giant covalent structuresProperties of metals and alloys, and why metals conductDiamond and graphiteGraphene and fullerenes
Chemical Analysis
Chemical Changes
Topic overviewThe reactivity seriesMetal oxides, extraction, and redox in terms of electronsAcids reacting with metals, neutralisation and saltsSoluble saltsThe pH scale and neutralisationStrong and weak acidsThe process of electrolysis, and molten ionic compoundsUsing electrolysis to extract metalsElectrolysis of aqueous solutionsRepresentation of reactions at electrodes as half equations
Chemistry of the Atmosphere
Topic overviewThe Earth's early atmosphereHow oxygen increased and carbon dioxide decreasedThe gases in today's atmosphere, and which are greenhouse gasesHuman activities which contribute to an increase in greenhouse gases in the atmosphereGlobal climate change and carbon footprintsAtmospheric pollutants from fuels, and their effects
Energy Changes
Organic Chemistry
Quantitative Chemistry
The Rate and Extent of Chemical Change
Topic overviewMeasuring the mean rate of a reactionRate from graphs, and the gradient of a tangentFactors which affect the rates of chemical reactionsCollision theory and activation energyCatalystsReversible reactions and dynamic equilibriumThe effect of changing conditions on equilibriumThe effect of changing concentrationThe effect of temperature changes on equilibriumThe effect of pressure changes on equilibrium
Atomic Structure and the Periodic Table
Relative atomic mass and electronic structure
- 3 things to know
- Chemistry Paper 1
Overview
Relative atomic mass as an average over isotopes, why chlorine is 35.5, calculating relative atomic mass from percentage abundances, how electrons fill the lowest energy levels or shells first, and writing electronic structures such as 2,8,1 for sodium and 2,8,7 for chlorine.
What you need to know
Answer each one before you reveal it.
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Key term
Describe the method for calculating a relative atomic mass from percentage abundances.
Key term
How many electrons fill the lowest energy level of an atom?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is the relative atomic mass of an element?
Model answer
It is an average value that takes account of the abundance of each isotope of the element.
- 2
Explain why the relative atomic mass of chlorine is 35.5 rather than a whole number.
Model answer
Because chlorine is a mixture of isotopes of mass 35 and 37, and the average weighted by their abundances falls between them.
- 3
Which two pieces of information about an element's isotopes are needed to find its relative atomic mass?
Model answer
The mass number of each isotope and the abundance of each isotope.
- 4
Describe the method for calculating a relative atomic mass from percentage abundances.
Model answer
Multiply each isotope's mass number by its percentage abundance, add the results together and divide by 100.
- 5
An element is 90% atoms of mass number 20 and 10% atoms of mass number 22. Calculate its relative atomic mass.
Model answer
It is 20.2, from (90 × 20 + 10 × 22) ÷ 100.
- 6
Boron is 20% boron-10 and 80% boron-11. Calculate the relative atomic mass of boron.
Model answer
It is 10.8, from (20 × 10 + 80 × 11) ÷ 100.
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