Key term
Edexcel GCSE Combined Science Chemistry 1SC0
Key Concepts in Chemistry
Topic overviewFormulae, word equations and balanced equationsHazard symbols and assessing riskThe changing model of the atomProtons, neutrons and electronsThe nucleus, mass number and atomic massElements and isotopesCalculating particle numbers and relative atomic massMendeleev's periodic tableHow the modern periodic table is arrangedElectronic configuration and the periodic tableHow ionic bonds formIons in ionic compoundsFormulae of ionic compoundsNaming compounds and the ionic latticeCovalent bonds and moleculesDot and cross diagrams for simple moleculesClassifying substances and the properties of ionic compoundsProperties of simple molecular substances, and forms of carbonGraphite and diamondFullerenes and graphenePolymers and models of bondingThe properties of metalsRelative formula mass and percentage compositionEmpirical and molecular formulaeConservation of mass in closed and open systemsReacting masses from balanced equationsConcentration in grams per cubic decimetre
States of Matter and Mixtures
Topic overviewThe three states of matter and changes of stateEnergy changes during changes of state, and predicting statePure substances and melting point dataChoosing a separation techniqueSeparating a mixture in practicePaper chromatography and interpreting a chromatogramInvestigating inks by distillation and chromatographyMaking water potable
Chemical Changes
Topic overviewAcids, alkalis and the pH scaleIndicators: litmus, methyl orange and phenolphthaleinInvestigating pH change when neutralising an acidBases and alkalisReactions of acids, and testing for hydrogen and carbon dioxideNeutralisation and its ionic equationPreparing soluble salts from insoluble and soluble reactantsPreparing pure, dry copper sulfate crystalsCarrying out an acid-alkali titrationSolubility rulesPredicting precipitates and preparing an insoluble saltElectrolytes and what electrolysis isMovement of ions and predicting the products of molten electrolysisElectrolysis with inert electrodesElectrolysis of copper sulfate solutionInvestigating the electrolysis of copper sulfate
Extracting Metals and Equilibria
Groups in the Periodic Table
Topic overviewThe groups of the periodic table, and the alkali metalsReactions of the alkali metals with waterThe pattern in alkali metal reactivity and why it happensPhysical properties of the halogensThe test for chlorine, and halogens reacting with metalsHydrogen halides, and explaining halogen reactivityDisplacement reactions of the halogensGroup 0: the noble gases
Rates of Reaction and Energy Changes
Fuels and Earth Science
Topic overviewHydrocarbons and crude oilFractional distillation and the fractionsProperties of the fractions and homologous seriesComplete and incomplete combustionCarbon monoxide and sootPollutants and acid rainHydrogen and fossil fuels comparedCracking and why it is necessaryThe Earth's early atmosphereHow the oceans formed and how oxygen appearedThe test for oxygen and the greenhouse gasesToday's atmosphere and evidence for climate change
Key Concepts in Chemistry
Calculating particle numbers and relative atomic mass
- 2 things to know
- Papers 3 and 4
Overview
Working out protons, neutrons and electrons from atomic and mass numbers, what relative atomic mass means, why chlorine's is 35.5 while fluorine's is almost exactly 19, and the isotope masses and abundances that decide it.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Why is the relative atomic mass of chlorine 35.5 rather than a whole number?
Questions from this subtopic
Each one with the model answer underneath.
- 1
An atom of sodium has atomic number 11 and mass number 23. State its numbers of protons, neutrons and electrons.
Model answer
It has 11 protons, 12 neutrons and 11 electrons.
- 2
An atom of chlorine has atomic number 17 and mass number 35. State its numbers of protons, neutrons and electrons.
Model answer
It has 17 protons, 18 neutrons and 17 electrons.
- 3
Potassium has atomic number 19 and mass number 39. How many neutrons are in the nucleus?
Model answer
There are 20 neutrons.
- 4
An atom contains 26 protons and 30 neutrons. State its atomic number and its mass number.
Model answer
Its atomic number is 26 and its mass number is 56.
- 5
An atom of fluorine has atomic number 9 and mass number 19. How many neutrons does it have, and how is this worked out?
Model answer
It has 10 neutrons, found by subtracting the atomic number from the mass number: 19 − 9 = 10.
- 6
An atom of carbon-14 has atomic number 6. State its numbers of protons, neutrons and electrons.
Model answer
It has 6 protons, 8 neutrons and 6 electrons.
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