Changing Models – Atomic Theory

As scientific understanding develops models and analogies are changed. Models are used by Scientists to predict what will happen in experiments so it is important they are updated. For example, as new evidence is discovered the atom model is changing.

Democritus

Year: 460 BC
Democritus devised the term atomos meaning indivisible.
He used an analogy of a lump of cheese.
- If you cut it in half and half again, eventually you will get to a point where it could not be cut any further.
He did not know what ‘they’ looked like.

John Dalton – The Billiard Ball Model

Year: 1803
Dalton said:
- That atomos make up elements that he called atoms
- Different elements have different atoms
- Atoms of the same element are identical
- Atoms can not be created or destroyed
- If you join different elements up they make compounds
He said these atoms were tiny and invisible.
Dalton used tiny balls as a model to explain his ideas this is often known as the Billiard Ball Model.

JJ (Joseph John) Thompson – The Plum Pudding Model

Year: From 1897
Thomson’s experiments discovered the electron.
He proposed that atoms where a ball of positive charge has negatively charged electrons embedded in it.
His model has been called the Plum Pudding Model.
- In America this is often called the Chocolate Chip Cookie Model.

Ernest Rutherford – The Nuclear Model

Year: 1911
Completed the gold foil alpha scattering experiment in which he fired alpha particles from radioactive sources.
Most alpha particles went straight through however few were scattered at different directions.
He found that the atom was:
- Mostly empty space.
- The middle of the atom is a solid mass called the nucleus.
- The nucleus is positively charged containing protons.
- Electrons surround the nucleus at a distance.
Rutherford’s model is known as the Nuclear Model.

Niels Bohr – The Planetary Model

Year: 1913
Discovered electrons orbit the nucleus at set distances and are arranged in shells or orbitals.
The first shell can fit two electrons, the second shell can fit eight electrons, the third shell can fit eight electrons
This model is called the Planetary Model

James Chadwick – The Quantum Model

Year: 1932
Chadwick discovered a particle with the same mass as a proton but with no charge.
- This is unlike the proton which has a positive charge.
He called these neutrons.
These are found in the nucleus.
This model is known as the Quantum Model.

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.2.1Reproduction in Humans

1.2.2Male Reproductive System

1.2.3Female Reproductive System

1.2.4Gestation

1.2.5Pregnancy

1.2.6Puberty

1.2.7The Menstrual Cycle

1.2.8Reproduction in Plants

1.2.9Pollination

1.2.10Dispersal Method

1.2.11Variation

1.2.12Causes of Variation

1.2.13Inheritance

1.2.14Adaptations and Evolution

1.2.15Species & Selective Breeding

1.2.16Genetic Conditions

1.2.17End of Topic Test - Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.4.1Balanced Diets

1.4.2Vitamins & Minerals

1.4.3Protein

1.4.4Lipids, Oils and Fats

1.4.5Carbohydrates

1.4.6Starch

1.4.7Energy Needs

1.4.8Dietary Fibre

1.4.9Diseases Caused by Nutritional Deficiencies

1.4.10Digestion

1.4.11Plant Nutrition

1.4.12Enzymes in Digestion

1.4.13Required Practical - Enzymes in Digestion

1.5Plants & Photosynthesis

1.5.1Roots

1.5.2Photosynthesis

1.5.3Leaves

1.5.4Rate of Photosynthesis

1.5.5Testing the Rate of Photosynthesis

1.5.6Water Transport in Plants

1.5.7Translocation

1.5.8The Carbon Cycle

1.5.9Human Activities & Carbon Dioxide

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.1.1Particles

2.1.2States of Matter

2.1.3Changes of State

2.1.4Properties of States of Matter

2.1.5Diffusion

2.1.6Changing State

2.1.7Pressure

2.1.8Temperature Increase in a Gas

2.1.9Conservation of Mass

2.1.10Purity of Substances

2.1.11Pure Substances

2.1.12Evaporation

2.1.13Mixtures

2.1.14Separating Mixtures

2.1.15Distillation

2.1.16Chromatography

2.1.17Solubility

2.1.18Investigating Solubility

2.2Chemical Reactions

2.2.1Chemical Reactions

2.2.2Common Reactions

2.2.3Acids & Alkalis

2.2.4Reactions of Acids

2.2.5Testing for Hydrogen

2.2.6The pH Scale

2.2.7Titration

2.2.8End of Topic Test - Chemical Reactions

2.3Atoms, Elements, Compounds

2.3.1Atoms

2.3.2Elements

2.3.3Compounds & Mixtures

2.3.4Electron Configuration

2.3.5Chemical Symbols

2.3.6Chemical Formulae

2.3.7Conservation of Mass

2.3.8Vacuums

2.3.9Molecules

2.3.10End of Topic Test - Particles & Atoms

2.4The Periodic Table

2.4.1Physical Properties

2.4.2Chemical Properties

2.4.3The Periodic Table

2.4.4Metals

2.4.5Non-Metals

2.4.6Alkali Metals

2.4.7Halogens

2.4.8Oxides

2.4.9End of Topic Test - The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.6.1Ions

2.6.2Ionic Bonding

2.6.3State Symbols

2.6.4Balancing Chemical Equations

2.6.5Relative Formula Mass

2.6.6Calculating the Relative Formula Mass

2.6.7The Reactivity Series

2.6.8Carbon & The Reactivity Series

2.6.9Displacement Reactions

2.6.10Displacement Reactions - Halogens

2.6.11Alloys

2.6.12Metal Alloys

2.7Energetics

2.7.1Measuring Gas Production

2.7.2Observing a Colour Change

2.7.3Analysing Reaction Rates

2.7.4Factors Affecting the Rate of Reaction

2.7.5Catalysts

2.7.6Testing for Oxygen

2.7.7Energy Changes During Reactions

2.8Properties of Materials

2.8.1Testing for Gases

2.8.2Alloys

2.8.3Density

2.8.4Density of Solids, Liquids & Gases HyperLearning

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.4.1Circuit Symbols

3.4.2Resistors & Diodes

3.4.3Electric Current

3.4.4Measuring Current

3.4.5Potential Difference

3.4.6Series Circuits

3.4.7Parallel Circuits

3.4.8Resistance

3.4.9Charges

3.4.10Static Electricity

3.4.11Magnets

3.4.12Magnetic Fields

3.4.13The Earth's Field

3.4.14Electromagnetism

3.4.15Uses of Electromagnets

3.4.16Strength of Magnetic Fields

3.4.17Circuit Symbols HyperLearning

3.5Matter

3.6Space Physics

3.6.1The Sun

3.6.2The Planets

3.6.3Other Astronomical Bodies

3.6.4The Milky Way

3.6.5Beyond The Milky Way

3.6.6The Seasons

3.6.7Days, Months & Years

3.6.8The Moon

3.6.9Light Years

3.6.10End of Topic Test - Space

4Thinking Scientifically

4.1Models & Representations

4.1.1Strengths & Limitations of Models

4.1.2Symbols & Formulae to Represent Scientific Ideas

4.1.3Analogies in Science

4.1.4Changing Models – Atomic Theory

4.1.5Working Safely in the Lab

4.1.6Variables

4.1.7Writing a Hypothesis & Prediction

4.1.8Planning an Experiment

4.1.9Maths Skills for Science

4.1.10Drawing Scientific Apparatus

4.1.11Observation & Measurement Skills

4.1.12Types of Data

4.1.13Graphs & Charts

4.1.14Bias in Science

4.1.15Conclude & Evaluate

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