3.1.6
Isotopes
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Isotopes
Atoms of the same element always have the same number of protons (or have the same atomic number). But atoms of the same element can have different numbers of neutrons: these atoms are known as isotopes. Hydrogen has 3 different isotopes:
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Protium
- Protium is a hydrogen atom with 1 proton and 0 neutrons.
- 99.98% of hydrogen atoms are protium.
- It is used in hydrogen fuel cells and the production of plastics.
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Deuterium
- Deuterium is a hydrogen atom with 1 proton and 1 neutron.
- Around 0.02% of hydrogen atoms are deuterium.
- It is used in nuclear fusion.

Tritium
- Tritium is a hydrogen atom with 1 proton and 2 neutrons.
- It is very rare.
- It is used in thermonuclear fusion weapons.
1States of Matter
2Elements, Compounds & Mixtures
2.1Elements, Mixtures & Compounds
2.1.1Elements & Compounds2.1.2Chemical Formula2.1.3Mixtures2.1.4Purity2.1.5Separating Mixtures2.1.6Separating Mixtures 22.1.7Paper Chromatography2.1.8Paper Chromatography Analysis2.1.9Paper Chromatography - Practical2.1.10End of Topic Test - Elements,Compounds,Mixtures2.1.11Grade 9 - Chromatography2.1.12Exam-Style Questions - Separation of Mixtures
3Atomic Structure
4The Periodic Table
5Chemical Formulae, Equations & Calculations
5.1Equations
5.1.1Forming Equations5.1.2Balancing Symbols5.1.3State Symbols5.1.4Relative Formula Mass5.1.5Calculating Relative Formula Mass5.1.6Relative Formula Mass - Calculations5.1.7Introducing Moles5.1.8Relative Formula Mass5.1.9Amounts of Substance5.1.10Moles & Yield5.1.11Moles - Calculations5.1.12Balancing Equations5.1.13Moles to Balance Equations5.1.14Limiting Reactants5.1.15Chemical Measurements5.1.16Calculating Mass5.1.17Changing Mass5.1.18Exam-Style Questions - Moles5.1.19Percentage Yield5.1.20Calculating Yield5.1.21Percentage Yield - Calculations5.1.22Empirical & Molecular Formula5.1.23Experiment for Empirical Formula5.1.24Empirical Formula - Calculations5.1.25Concentrations & Amounts5.1.26Conclusion of Solutions5.1.27Volumes and Gases5.1.28Concentration & Amounts - Calculations5.1.29End of Topic Test - Equations5.1.30Grade 9 - Equations
6Bonding
6.1Ionic Bonding
6.2Covalent Bonding
6.2.1Covalent Bonding6.2.2Dot-and-Cross Diagrams6.2.3Representing Covalent Bonds6.2.4Covalent Bond Examples6.2.5Covalent Bond Examples 26.2.6Simple Covalent Molecules6.2.7Chemical Properties of Small Molecules6.2.8Giant Covalent Structures6.2.9Giant Covalent Structures 26.2.10Carbon Structures - Diamonds6.2.11Carbon Structures - Graphite6.2.12Carbon Structures - Fullerenes6.2.13Carbon Structures - Summary6.2.14Exam-Style Questions - Allotropes of Carbon
7Electrolysis
8Groups of the Periodic Table
8.1Alkali Metals & Halogens
8.1.1Alkali Metals8.1.2Alkali Metals - Properties8.1.3Alkali Metal Reactions8.1.4Reactivity of Alkali Metals8.1.5Halogens - Properties8.1.6Halogens - Colours and States8.1.7Halogen - Displacement Reactions8.1.8Halogen - Displacement Reactions 28.1.9Reactions Between Halogens and Metals8.1.10Hydrogen Halides8.1.11End of Topic Test - Alkali Metals & Halogens8.1.12Grade 9 - Alkali Metals & Halogens8.1.13Exam-Style Questions - Alkali Metals
9The Atmosphere
9.1Gases in the Atmosphere
9.1.1Gases in the Air9.1.2Calculating Oxygen in the Air - Metal9.1.3Calculating Oxygen in the Air - Non-Metal9.1.4Oxygen9.1.5Carbon Dioxide9.1.6Greenhouse Gases9.1.7Greenhouse Gases & Human Activities9.1.8Greenhouse Gases & Climate9.1.9End of Topic Test - Gases in the Atmosphere9.1.10Grade 9 - Gases in the Atmosphere
10Reactivity Series
10.1Reactivity Series
10.1.1Reactivity Diagram10.1.2Displacement Reactions10.1.3Reactivity Tests - Water10.1.4Reactivity Tests - Acid10.1.5Reactivity Tests - Metals10.1.6Corrosion10.1.7Preventing Corrosion10.1.8Metal Oxide10.1.9Oxidisation & Reduction10.1.10Redox Reactions10.1.11End of Topic Test - Reactivity Series10.1.12Grade 9 - Reactivity Series10.1.13Exam-Style Questions - Redox Reactions
11Metal Extraction
12Acids & Alkalis
12.1Acids, Alkalis & Titrations
12.1.1Acids and Alkali Indicators12.1.2Is it an Acid or Alkali?12.1.3The pH Scale12.1.4Titrations12.1.5Titration - Practical12.1.6Titrations - Methods12.1.7Soluble Salts12.1.8Solubility of Salts12.1.9Making Insoluble Salts12.1.10Required Practical: Separating Mixtures12.1.11Reaction of Acid & Metals12.1.12Neutralisation of Acids12.1.13Strong vs Weak Bases12.1.14End of Topic Test - Acids & Alkalis12.1.15Grade 9 - Acids & Alkalis12.1.16Exam-Style Questions - Neutralisation & Titrations
13Chemical Tests
13.1Identifying Gases
13.2Testing Anions, Cations & Water
13.2.1Flame Tests13.2.2Flame Test - Practical13.2.3Metal Hydroxides13.2.4Testing Cations13.2.5Testing for Aqueous Cations13.2.6Testing Carbonates13.2.7Testing Halides13.2.8Testing for Carbonate and Halides13.2.9Testing Sulfates13.2.10Testing Sulfates 213.2.11Testing Water13.2.12Testing Water Purity13.2.13End of Topic Test - Chemical Tests13.2.14Grade 9 - Chemical Tests13.2.15Exam-Style Questions - Identifying Gases & Ions
14Physical Chemistry
14.1Energetics
14.1.1Energy Conservation14.1.2Exothermic Reactions14.1.3Endothermic Reactions14.1.4Heat Changes14.1.5Calculating Heat Energy Transferred14.1.6Molar Enthalpy Change14.1.7Reaction Profiles14.1.8Reaction Profiles - Catalysed vs Uncatalysed14.1.9Exam-Style Questions - Reaction Profiles14.1.10Chemical Bonds14.1.11Bond Energies
14.2Rates of Reaction
15Organic Chemistry
15.1Hydrocarbons
15.2Alkanes & Alkenes
15.3Alcohols
15.4Carboxylic Acids
15.5Esters
15.6Synthetic Polymers
15.7End of Topic - Organic Chemistry
Jump to other topics
1States of Matter
2Elements, Compounds & Mixtures
2.1Elements, Mixtures & Compounds
2.1.1Elements & Compounds2.1.2Chemical Formula2.1.3Mixtures2.1.4Purity2.1.5Separating Mixtures2.1.6Separating Mixtures 22.1.7Paper Chromatography2.1.8Paper Chromatography Analysis2.1.9Paper Chromatography - Practical2.1.10End of Topic Test - Elements,Compounds,Mixtures2.1.11Grade 9 - Chromatography2.1.12Exam-Style Questions - Separation of Mixtures
3Atomic Structure
4The Periodic Table
5Chemical Formulae, Equations & Calculations
5.1Equations
5.1.1Forming Equations5.1.2Balancing Symbols5.1.3State Symbols5.1.4Relative Formula Mass5.1.5Calculating Relative Formula Mass5.1.6Relative Formula Mass - Calculations5.1.7Introducing Moles5.1.8Relative Formula Mass5.1.9Amounts of Substance5.1.10Moles & Yield5.1.11Moles - Calculations5.1.12Balancing Equations5.1.13Moles to Balance Equations5.1.14Limiting Reactants5.1.15Chemical Measurements5.1.16Calculating Mass5.1.17Changing Mass5.1.18Exam-Style Questions - Moles5.1.19Percentage Yield5.1.20Calculating Yield5.1.21Percentage Yield - Calculations5.1.22Empirical & Molecular Formula5.1.23Experiment for Empirical Formula5.1.24Empirical Formula - Calculations5.1.25Concentrations & Amounts5.1.26Conclusion of Solutions5.1.27Volumes and Gases5.1.28Concentration & Amounts - Calculations5.1.29End of Topic Test - Equations5.1.30Grade 9 - Equations
6Bonding
6.1Ionic Bonding
6.2Covalent Bonding
6.2.1Covalent Bonding6.2.2Dot-and-Cross Diagrams6.2.3Representing Covalent Bonds6.2.4Covalent Bond Examples6.2.5Covalent Bond Examples 26.2.6Simple Covalent Molecules6.2.7Chemical Properties of Small Molecules6.2.8Giant Covalent Structures6.2.9Giant Covalent Structures 26.2.10Carbon Structures - Diamonds6.2.11Carbon Structures - Graphite6.2.12Carbon Structures - Fullerenes6.2.13Carbon Structures - Summary6.2.14Exam-Style Questions - Allotropes of Carbon
7Electrolysis
8Groups of the Periodic Table
8.1Alkali Metals & Halogens
8.1.1Alkali Metals8.1.2Alkali Metals - Properties8.1.3Alkali Metal Reactions8.1.4Reactivity of Alkali Metals8.1.5Halogens - Properties8.1.6Halogens - Colours and States8.1.7Halogen - Displacement Reactions8.1.8Halogen - Displacement Reactions 28.1.9Reactions Between Halogens and Metals8.1.10Hydrogen Halides8.1.11End of Topic Test - Alkali Metals & Halogens8.1.12Grade 9 - Alkali Metals & Halogens8.1.13Exam-Style Questions - Alkali Metals
9The Atmosphere
9.1Gases in the Atmosphere
9.1.1Gases in the Air9.1.2Calculating Oxygen in the Air - Metal9.1.3Calculating Oxygen in the Air - Non-Metal9.1.4Oxygen9.1.5Carbon Dioxide9.1.6Greenhouse Gases9.1.7Greenhouse Gases & Human Activities9.1.8Greenhouse Gases & Climate9.1.9End of Topic Test - Gases in the Atmosphere9.1.10Grade 9 - Gases in the Atmosphere
10Reactivity Series
10.1Reactivity Series
10.1.1Reactivity Diagram10.1.2Displacement Reactions10.1.3Reactivity Tests - Water10.1.4Reactivity Tests - Acid10.1.5Reactivity Tests - Metals10.1.6Corrosion10.1.7Preventing Corrosion10.1.8Metal Oxide10.1.9Oxidisation & Reduction10.1.10Redox Reactions10.1.11End of Topic Test - Reactivity Series10.1.12Grade 9 - Reactivity Series10.1.13Exam-Style Questions - Redox Reactions
11Metal Extraction
12Acids & Alkalis
12.1Acids, Alkalis & Titrations
12.1.1Acids and Alkali Indicators12.1.2Is it an Acid or Alkali?12.1.3The pH Scale12.1.4Titrations12.1.5Titration - Practical12.1.6Titrations - Methods12.1.7Soluble Salts12.1.8Solubility of Salts12.1.9Making Insoluble Salts12.1.10Required Practical: Separating Mixtures12.1.11Reaction of Acid & Metals12.1.12Neutralisation of Acids12.1.13Strong vs Weak Bases12.1.14End of Topic Test - Acids & Alkalis12.1.15Grade 9 - Acids & Alkalis12.1.16Exam-Style Questions - Neutralisation & Titrations
13Chemical Tests
13.1Identifying Gases
13.2Testing Anions, Cations & Water
13.2.1Flame Tests13.2.2Flame Test - Practical13.2.3Metal Hydroxides13.2.4Testing Cations13.2.5Testing for Aqueous Cations13.2.6Testing Carbonates13.2.7Testing Halides13.2.8Testing for Carbonate and Halides13.2.9Testing Sulfates13.2.10Testing Sulfates 213.2.11Testing Water13.2.12Testing Water Purity13.2.13End of Topic Test - Chemical Tests13.2.14Grade 9 - Chemical Tests13.2.15Exam-Style Questions - Identifying Gases & Ions
14Physical Chemistry
14.1Energetics
14.1.1Energy Conservation14.1.2Exothermic Reactions14.1.3Endothermic Reactions14.1.4Heat Changes14.1.5Calculating Heat Energy Transferred14.1.6Molar Enthalpy Change14.1.7Reaction Profiles14.1.8Reaction Profiles - Catalysed vs Uncatalysed14.1.9Exam-Style Questions - Reaction Profiles14.1.10Chemical Bonds14.1.11Bond Energies
14.2Rates of Reaction
15Organic Chemistry
15.1Hydrocarbons
15.2Alkanes & Alkenes
15.3Alcohols
15.4Carboxylic Acids
15.5Esters
15.6Synthetic Polymers
15.7End of Topic - Organic Chemistry
Practice questions on Isotopes
Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.
- 1What are the 3 isotopes of hydrogen?Fill in the list
- 2How many protons do hydrogen atoms contain?Multiple choice
- 3
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- 5
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