Relative Atomic Mass

Relative Atomic Mass (A_r)

The relative atomic mass (A_r) is the average mass of all of the isotopes of an element. It takes into account how often each isotope is found (the isotope abundance).

Illustrative background for Calculating relative atomic masses (A<sub>r</sub>)

Illustrative background for Calculating relative atomic masses (A<sub>r</sub>) ?? "content

Calculating relative atomic masses (A_r)

We can calculate relative atomic masses (A_r) using the expression shown above.

Equation explained

The Σ means 'sum of'.
The numerator is 'the sum of the isotope abundance times the isotope mass'.
The denominator is 'the sum of all the isotope abundances'.

Illustrative background for E.g. a<sub>r</sub> of chlorine

Illustrative background for E.g. a<sub>r</sub> of chlorine ?? "content

E.g. a_r of chlorine

Cl may exist as 2 isotopes, ³⁵Cl and ³⁷Cl.
Isotope abundances:
- 75% ³⁵Cl
- 25% ³⁷Cl
  - A_r = (0.75 x 35) + (0.25 x 37) = 35.5.
The existence of isotopes means that the relative atomic mass is not always a whole number.

1States of Matter

1.1States of Matter

1.1.1States of Matter

1.1.2Simple Sphere

1.1.3Changes of State

1.1.4Changes of State 2

1.1.5Changes of State 3

1.1.6Changes of State and Temperature

1.1.7Solubility

1.1.8Solubility Curves

1.1.9Solubility - Experiments

1.1.10Diffusion - Experiment

1.1.11Changing State HyperLearning

2Elements, Compounds & Mixtures

2.1Elements, Mixtures & Compounds

2.1.1Elements & Compounds

2.1.2Chemical Formula

2.1.3Mixtures

2.1.4Purity

2.1.5Separating Mixtures

2.1.6Separating Mixtures 2

2.1.7Paper Chromatography

2.1.8Paper Chromatography Analysis

2.1.9Paper Chromatography - Practical

2.1.10End of Topic Test - Elements,Compounds,Mixtures

2.1.11Grade 9 - Chromatography

2.1.12Exam-Style Questions - Separation of Mixtures

3Atomic Structure

3.1Atoms

3.1.1Atomic Structure

3.1.2Atom Size

3.1.3Subatomic Particles

3.1.4Atomic Number

3.1.5Relative Atomic Mass

3.1.6Isotopes

3.1.7Isotopes 2

4The Periodic Table

4.1The Periodic Table

4.1.1Periodic Table Arrangement

4.1.2Electron Structure

4.1.3Metals & Non-Metals

4.1.4Noble Gases

4.1.5End of Topic Test- Atomic Structure,Periodic Table

4.1.6Grade 9 - Atomic Structure, Periodic Table

4.1.7Exam-Style Questions -Alkali Metals

5Chemical Formulae, Equations & Calculations

5.1Equations

5.1.1Forming Equations

5.1.2Balancing Symbols

5.1.3State Symbols

5.1.4Relative Formula Mass

5.1.5Calculating Relative Formula Mass

5.1.6Relative Formula Mass - Calculations

5.1.7Introducing Moles

5.1.8Relative Formula Mass

5.1.9Amounts of Substance

5.1.10Moles & Yield

5.1.11Moles - Calculations

5.1.12Balancing Equations

5.1.13Moles to Balance Equations

5.1.14Limiting Reactants

5.1.15Chemical Measurements

5.1.16Calculating Mass

5.1.17Changing Mass

5.1.18Exam-Style Questions - Moles

5.1.19Percentage Yield

5.1.20Calculating Yield

5.1.21Percentage Yield - Calculations

5.1.22Empirical & Molecular Formula

5.1.23Experiment for Empirical Formula

5.1.24Empirical Formula - Calculations

5.1.25Concentrations & Amounts

5.1.26Conclusion of Solutions

5.1.27Volumes and Gases

5.1.28Concentration & Amounts - Calculations

5.1.29End of Topic Test - Equations

5.1.30Grade 9 - Equations

6Bonding

6.1Ionic Bonding

6.1.1Dot & Cross Diagrams

6.1.2Changes in Number of Subatomic Particles

6.1.3Ionic Bonding

6.1.4Ions

6.1.5Types of Bonding

6.1.6Ion Formation

6.1.7Identifying Ionic Compounds

6.1.8Ionic Compounds

6.1.9Ionic and Metallic Bonding

6.1.10Ion Charges

6.2Covalent Bonding

6.2.1Covalent Bonding

6.2.2Dot-and-Cross Diagrams

6.2.3Representing Covalent Bonds

6.2.4Covalent Bond Examples

6.2.5Covalent Bond Examples 2

6.2.6Simple Covalent Molecules

6.2.7Chemical Properties of Small Molecules

6.2.8Giant Covalent Structures

6.2.9Giant Covalent Structures 2

6.2.10Carbon Structures - Diamonds

6.2.11Carbon Structures - Graphite

6.2.12Carbon Structures - Fullerenes

6.2.13Carbon Structures - Summary

6.2.14Exam-Style Questions - Allotropes of Carbon

6.3Metallic Bonding

6.3.1Metallic Bonding

6.3.2Metals as Conductors

6.3.3Pure Metals

6.3.4End of Topic Test - Bonding

6.3.5Grade 9 - Bonding

6.3.6Exam-Style Questions - Metals

7Electrolysis

7.1Electrolysis

7.1.1Molten Ionic Compounds

7.1.2Electrolysis - Process

7.1.3Electrolysis - Aqueous Solutions

7.1.4Electrolysis - Copper Sulfate

7.1.5Electrolysis - Examples

7.1.6Half Equations

7.1.7Exam-Style Questions - Electrolysis

8Groups of the Periodic Table

8.1Alkali Metals & Halogens

8.1.1Alkali Metals

8.1.2Alkali Metals - Properties

8.1.3Alkali Metal Reactions

8.1.4Reactivity of Alkali Metals

8.1.5Halogens - Properties

8.1.6Halogens - Colours and States

8.1.7Halogen - Displacement Reactions

8.1.8Halogen - Displacement Reactions 2

8.1.9Reactions Between Halogens and Metals

8.1.10Hydrogen Halides

8.1.11End of Topic Test - Alkali Metals & Halogens

8.1.12Grade 9 - Alkali Metals & Halogens

8.1.13Exam-Style Questions - Alkali Metals

9The Atmosphere

9.1Gases in the Atmosphere

9.1.1Gases in the Air

9.1.2Calculating Oxygen in the Air - Metal

9.1.3Calculating Oxygen in the Air - Non-Metal

9.1.4Oxygen

9.1.5Carbon Dioxide

9.1.6Greenhouse Gases

9.1.7Greenhouse Gases & Human Activities

9.1.8Greenhouse Gases & Climate

9.1.9End of Topic Test - Gases in the Atmosphere

9.1.10Grade 9 - Gases in the Atmosphere

10Reactivity Series

10.1Reactivity Series

10.1.1Reactivity Diagram

10.1.2Displacement Reactions

10.1.3Reactivity Tests - Water

10.1.4Reactivity Tests - Acid

10.1.5Reactivity Tests - Metals

10.1.6Corrosion

10.1.7Preventing Corrosion

10.1.8Metal Oxide

10.1.9Oxidisation & Reduction

10.1.10Redox Reactions

10.1.11End of Topic Test - Reactivity Series

10.1.12Grade 9 - Reactivity Series

10.1.13Exam-Style Questions - Redox Reactions

11Metal Extraction

11.1Metal Extraction

11.1.1Extracting Metals

11.1.2Extracting Metals - Electrolysis

11.1.3Alloys

11.1.4Metal Alloys

11.1.5End of Topic Test - Extracting Metals

11.1.6Grade 9 - Extracting Metals

12Acids & Alkalis

12.1Acids, Alkalis & Titrations

12.1.1Acids and Alkali Indicators

12.1.2Is it an Acid or Alkali?

12.1.3The pH Scale

12.1.4Titrations

12.1.5Titration - Practical

12.1.6Titrations - Methods

12.1.7Soluble Salts

12.1.8Solubility of Salts

12.1.9Making Insoluble Salts

12.1.10Required Practical: Separating Mixtures

12.1.11Reaction of Acid & Metals

12.1.12Neutralisation of Acids

12.1.13Strong vs Weak Bases

12.1.14End of Topic Test - Acids & Alkalis

12.1.15Grade 9 - Acids & Alkalis

12.1.16Exam-Style Questions - Neutralisation & Titrations

13Chemical Tests

14Physical Chemistry

14.1Energetics

14.1.1Energy Conservation

14.1.2Exothermic Reactions

14.1.3Endothermic Reactions

14.1.4Heat Changes

14.1.5Calculating Heat Energy Transferred

14.1.6Molar Enthalpy Change

14.1.7Reaction Profiles

14.1.8Reaction Profiles - Catalysed vs Uncatalysed

14.1.9Exam-Style Questions - Reaction Profiles

14.1.10Chemical Bonds

14.1.11Bond Energies

14.2Rates of Reaction

14.2.1Reaction Practicals - Measuring Gas Production

14.2.2Reaction Practicals - Observing a Colour Change

14.2.3Rate of Reaction - Collision Theory

14.2.4Rate of Reaction - Key Factors

14.2.5Rate of Reaction - Catalysts

14.2.6End of Topic Test - Energetics & Rates

14.2.7Grade 9 - Energetics & Rates

14.3Reversible Reactions & Equilibria

14.3.1Reversible Reactions

14.3.2Dynamic Equilibrium

14.3.3Conditions and Equilibrium

14.3.4Equilibrium Position - Temperature

14.3.5Equilibrium Position - Pressure

14.3.6End of Topic Test - Equilibria

15Organic Chemistry

15.1Hydrocarbons

15.1.1Crude Oil

15.1.2Properties of Hydrocarbons

15.1.3Fractional Distillation

15.1.4Process of Fractional Distillation

15.1.5Fractions

15.1.6Combustion of Hydrocarbons

15.1.7Impurities

15.1.8Heavy Fractions of Crude Oil

15.1.9Cracking

15.2Alkanes & Alkenes

15.2.1Homologous Series

15.2.2Alkanes

15.2.3Smallest Alkanes

15.2.4Structural Isomerism

15.2.5Structure of Alkenes

15.2.6The Shortest Alkenes

15.2.7Alkene Reactions

15.2.8Types of Alkene Reactions

15.2.9Q5 - Alkene Reactions

15.3Alcohols

15.3.1Alcohols

15.3.2Smallest Alcohols

15.3.3Combustion of Alcohols

15.3.4Oxidisation of Ethanol

15.3.5Fermentation

15.3.6Ethanol Hydration

15.3.7Fermentation vs Hydration of Ethene

15.4Carboxylic Acids

15.4.1Carboxylic Acids

15.4.2Smallest Carboxylic Acids

15.4.3Reactions of Carboxylic Acids

15.5Esters

15.5.1Esters

15.5.2Ethyl Ethanoate

15.6Synthetic Polymers

15.6.1Polymers

15.6.2Addition Polymerisation

15.6.3Examples of Addition Polymerisation

15.6.4Problems With Polymers

15.6.5Condensation Polymerisation

15.7End of Topic - Organic Chemistry

15.7.1End of Topic Test - Organic Chemistry

15.7.2Grade 9 - Organic Chemistry

15.7.3Exam-Style Questions - Organic Compounds

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