1.1.6

Atom Size & Number

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Atoms and Sub-Atomic Particles

Atoms are tiny and very light. They are made up of sub-atomic particles (protons, neutrons, and electrons), which are even smaller and lighter than an atom.

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How big are atoms?

  • The radius of atoms is approximately 0.1 nanometres, or 1x10-10 m.
    • About 5 million hydrogen atoms could fit into a pinhead.
  • The nucleus of an atom is 10,000 times smaller than the atom.
    • If an atom was the size of Wembley Stadium, then the nucleus would be the size of a garden pea.
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Relative mass

  • Sub-atomic particles:
    • Relative mass of protons and neutrons = 1
    • Relative mass of electrons = 0.0005 (this gets rounded to zero)
  • Atoms:
    • Relative mass = number of protons + number of neutrons

Atomic Number and Mass Number

The atomic number is the number of protons in the atom. The mass number of an atom (or relative mass) is calculated by adding the number of protons and neutrons found in a nucleus. These numbers can be found for each element in the periodic table.

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Sodium

  • Mass number (top) = 23.
  • Atomic number (bottom) = 11.
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Carbon

  • Mass number (top) = 12.
  • Atomic number (bottom) = 6.

Jump to other topics

1Atomic Structure

1.1Atoms & Elements

1.1.1Elements & Compounds

1.1.2Chemical Reactions & Equations

1.1.3Mixtures

1.1.4Separating Mixtures

1.1.5Model of the Atom

1.1.6Atom Size & Number

1.1.7Atomic Number - Calculations

1.1.8Isotopes

1.1.9Isotopes HyperLearning

1.1.10Isotopes - Calculations

1.1.11Relative Atomic Mass

1.1.12Electron Structure

1.1.13Periodic Table

1.1.14Metals & Non-Metals

1.1.15Noble Gases

1.1.16Halogens

1.1.17Alkali Metals

1.1.18Transition Metals

1.1.19End of Topic Test - Atomic Structure

1.1.20Grade 9 - Atoms & Elements

1.1.21Exam-Style Questions - Atomic Structure

1.1.22Application Questions - Atomic Structure

2Chemical Bonding

2.1Chemical Bonds

2.1.1Types of Bonds

2.1.2Ionic Bonds

2.1.3Ionic Compounds

2.1.4Covalent & Metallic Bonds

2.1.5Representing Covalent Bonds

2.1.6Dots-And-Cross Diagrams

2.1.7Exam-Style Questions - Chemical Bonds

2.2States of Matter

2.2.1States of Matter

2.2.2Changing State

2.2.3Changing State HyperLearning

2.2.4State Symbols

2.2.5Exam-Style Questions - States of Matter

2.3Chemical Properties

2.3.1Chemical Properties of Ionic Compounds

2.3.2Chemical Properties of Small Molecules

2.3.3Molecular Forces & Polymers

2.3.4Metals & Giant Covalent Structures

2.3.5Alloys & Conductors

2.3.6Carbon Structures - Diamond & Graphite

2.3.7Carbon Structures - Graphene & Fullerenes

2.3.8Carbon Structures - Summary

2.3.9Nanoparticles

2.3.10Nanotechnology

2.3.11Surface Area to Volume Ratio & Nanotechnology Uses

2.3.12End of Topic Test - Chemical Bonding

2.3.13Grade 9 - Bonding & Structure

2.3.14Exam-Style Questions - Allotropes of Carbon

3Quantitative Chemistry

3.1Chemical Measurements

3.1.1Conservation of Mass

3.1.2Relative Formula Mass

3.1.3Relative Formula Mass - Calculations

3.1.4Measuring Mass

3.1.5Equations & Formula

3.1.6Moles 1

3.1.7Moles 2

3.1.8Moles 3

3.1.9Moles - Calculations

3.1.10Percentage Yield

3.1.11Percentage Yield - Calculations

3.1.12Moles & Yield

3.1.13Atom Economy

3.1.14Atom Economy - Calculations

3.1.15Concentrations & Amounts

3.1.16Amount of Substance in Relation to Volumes and Gas

3.1.17Concentrations & Amounts - Calculations

3.1.18Empirical Formula - Calculations

3.1.19End of Topic Test - Quant Chemistry

3.1.20Grade 9 - Quantitative Chemistry

3.1.21Exam-Style Questions - Moles

4Chemical Changes

4.1Acids, Alkalis & Redox Reactions

4.1.1Acids & Alkalis

4.1.2Redox Reactions

4.2Reactivity of Metals

4.2.1Reactivity Diagram

4.2.2Displacement Reactions

4.2.3Reactions with Water & Acid

4.2.4Reactivity Tests

4.2.5Extraction of Metals

4.2.6Exam-Style Questions - Displacement Reactions

4.3Reactions of Acids

4.3.1Reactions of Metals with Acids

4.3.2Neutralisation of Acids

4.3.3Soluble Salts

4.3.4Required Practical: Separating Mixtures

4.3.5The pH Scale

4.3.6Measuring pH

4.3.7Neutralisation & Titrations 1

4.3.8Neutralisation & Titrations 2

4.3.9Strong and Weak Acids

4.4Electrolysis

4.4.1Electrolysis

4.4.2Metal Extraction

4.4.3Electrolysis of Aqueous Solutions & Half Equations

4.4.4End of Topic Test - Chemical Changes

4.4.5Grade 9 - Chemical Changes

4.4.6Exam-Style Questions - Electrolysis

5Energy Changes

5.1Exothermic & Endothermic Reactions

5.1.1Energy Conservation

5.1.2Exothermic & Endothermic Reactions

5.1.3Reaction Profiles

5.1.4Reaction Profiles 2

5.2Chemical Cells & Fuel Cells

5.2.1Chemical Cells

5.2.2Batteries & Charging of Cells

5.2.3Fuel Cells

5.2.4Hydrogen Fuel Cell

5.2.5End of Topic Test - Energy Changes

5.2.6Grade 9 - Energy Changes

5.2.7Exam-Style Questions - Fuel Cells

6The Rate & Extent of Chemical Change

6.1Rate of Reaction

6.1.1Chemical Reactions

6.1.2Collision Theory

6.1.3Catalysts

6.1.4Catalysts in Industry

6.2Reversible Reactions

6.2.1Reversible Reactions

6.2.2Equilibrium

6.2.3Equilibrium Position

6.2.4Equilibrium Position 2

6.2.5End of Topic Test - Rates of Reaction

6.2.6Grade 9 - Rate & Extent of Chemical Change

6.2.7Exam-Style Questions - Reversible Reactions

7Organic Chemistry

7.1Carbon Compounds

7.1.1Crude Oil

7.1.2Alkanes

7.1.3Fractional Distillation

7.1.4Homologous Series

7.1.5Burning Hydrocarbons

7.1.6Cracking

7.1.7Uses of Alkenes

7.1.8Exam-Style Questions - Organic Compounds

7.2Alkenes & Alcohols

7.2.1Structure of Alkenes

7.2.2Reactions of Alkenes

7.2.3End of Topic Test - Alkanes & Alkenes

7.2.4Alcohols

7.2.5Reactions of Alcohols

7.2.6Carboxylic Acids

7.2.7Reactions of Carboxylic Acids

7.2.8Addition Polymers

7.2.9Condensation Polymers

7.2.10Naturally Occurring Polymers - Proteins

7.2.11Naturally Occurring Polymers - DNA & Sugars

7.2.12End of Topic Test - Alcohols, Acids & Polymers

7.2.13Grade 9 - Organic Chemistry

7.2.14Exam-Style Questions - Alcohols

8Chemical Analysis

8.1Purity, Formulations & Chromatography

8.1.1Purity & Formulations

8.1.2Chromatography

8.1.3Paper Chromatography 1

8.1.4Paper Chromatography 2

8.1.5Required Practical - Paper Chromatography

8.2Identification of Common Gases

8.2.1Identification of Hydrogen & Oxygen

8.2.2Identification of Carbon Dioxide & Chlorine

8.3Identifying Ions

8.3.1Flame Tests

8.3.2Required Practical: Flame Tests

8.3.3Metal Hydroxides

8.3.4Carbonates

8.3.5Halides, Sulfates

8.3.6Methodology for Chemical Analysis

8.3.7Flame Emission Spectroscopy

8.3.8End of Topic Test - Chemical Analysis

8.3.9Grade 9 - Chemical Analysis

8.3.10Exam-Style Questions - Identification of ions

9Chemistry of the Atmosphere

9.1The Earth's Atmosphere

9.1.1Proportions of Gases in the Atmosphere

9.1.2Oxygen & Carbon Dioxide in the Atmosphere

9.1.3Greenhouse Gases & Human Activities

9.1.4Greenhouse Gases & Human Activities

9.1.5Greenhouse Gases & Climate Change

9.1.6Carbon Footprints

9.1.7Common Atmospheric Pollutants & Their Properties

9.1.8End of Topic Test - The Earth

9.1.9Grade 9 - Chemistry of the Atmosphere

9.1.10Exam-Style Questions - Earth's Atmosphere

10Using Resources

10.1Using the Earth's Resources

10.1.1Potable Water & its Sources

10.1.2Potable Water in the UK & in Saudi Arabia

10.1.3Natural Resources

10.1.4Waste Water

10.1.5Metal Ore Extraction & the Properties of Copper

10.1.6Overexploitation & Alternative Extraction Methods

10.2Life Cycle Assessments & Recycling

10.2.1Life Cycle Assessments

10.2.2Difficulties with LCA

10.2.3Reducing Resource Usage

10.2.4Reducing Use of Metal and Glass

10.2.5Exam-Style Questions - Life Cycle Assessments

10.3Using Materials

10.3.1Corrosion

10.3.2Alloys

10.3.3Ceramics

10.3.4Polymers & Composites

10.4The Haber Process & NPK Fertilisers

10.4.1The Haber Process

10.4.2The Haber Process - Equation & Trade-Offs

10.4.3Formulated vs Manure Fertilisers

10.4.4NPK Fertilisers 1

10.4.5NPK Fertilisers 2

10.4.6End of Topic Test - Resources

10.4.7Grade 9 - Using Resources

10.4.8Exam-Style Questions - The Haber Process

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Model of the Atom

Atomic Number - Calculations