3.1.2
Atomic Structure 2
The Scattering of Alpha Particles
The Scattering of Alpha Particles
Ernest Rutherford discovered the nucleus by firing a beam of alpha particles at thin metal foils (only a few atoms wide).
Rutherford's experiment
Rutherford's experiment
- Most alpha particles passed straight through the foil.
- This suggested that most of the atom is made up of empty space.
- However, some particles bounced back towards the source.
Rutherford's conclusions
Rutherford's conclusions
- The large deflections suggested that some positively charged mass in the atom was repelling the particles.
- This led to the model of the atom with negatively charged electrons orbiting a positively charged nucleus.
The Model of the Atom
The Model of the Atom
Our understanding of atoms has improved over time. The models that we have used to understand atoms have also changed.
Thomson's plum pudding model
Thomson's plum pudding model
- In 1897, an English physicist called J. J. Thomson discovered electrons.
- He modelled the atom as a 'plum pudding' - a ball of positive charge (dough), with negatively charged electrons (currants) mixed in with the 'dough'.
Rutherford's nuclear model
Rutherford's nuclear model
- In 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms.
- He concluded that an atom's mass is concentrated in the atom's centre. This was called the "nucleus" and it contained positively charged particles called protons.
The modern model
The modern model
- Niels Bohr discovered that electrons orbit (fly around) the nucleus at fixed distances.
- In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons.
Electron Arrangements
Electron Arrangements
Electrons are arranged in shells around a nucleus. Each shell has a different energy level. When an atom absorbs or emits electromagnetic radiation, its electron arrangements can change.
Absorb radiation
Absorb radiation
- When atoms absorb electromagnetic radiation, electrons move to a higher energy level further away from the nucleus.
Emit radiation
Emit radiation
- When atoms emit electromagnetic radiation, electrons can drop to a lower energy level, closer to the nucleus.
1Energy
1.1Energy Changes
1.1.1Energy Stores
1.1.2Calculating Changes in Energy
1.1.3Changes in Kinetic Energy - Calculations
1.1.4Changes in GPE - Calculations
1.1.5Changes in EPE - Calculations
1.1.6Energy Transfers
1.1.7Mechanical Work Done
1.1.8Mechanical Work - Calculations
1.1.9Electrical Work Done
1.1.10Electrical Work Done- Calculations
1.2Energy Losses & Efficiency
2Electricity
2.1Electric Charge
2.2Resistance & Electrical Work
2.3Electric Circuits
2.4Electricity in Homes
2.5Static Electricity
3Particle Model of Matter
3.1States of Matter
3.2Heat
4Atoms & Radiation
4.1Atoms
4.2Radiation
4.2.1Radioactive Decay
4.2.2Radioactive Decay 2
4.2.3Types of Radioactive Emission
4.2.4Fission & Fusion
4.2.5Radioactive Decay Equations
4.2.6Radio. decay equations - Calculations
4.2.7Half Lives & Ionising Radiation
4.2.8Half Life - Calculations
4.2.9Uses & Dangers of Radiation
4.2.10Uses & Dangers of Radiation 2
4.2.11End of Topic Test - Atoms & Radiation
4.2.12Grade 9 - Radiation
4.2.13Exam-Style Questions - Radioactive Decay
5Forces
5.1Basics of Motion
5.2Forces
5.2.1Gravity
5.2.2Gravity - Calculations
5.2.3Resultant Forces
5.2.4Newton Second Law - Calculations
5.2.5Force Diagrams
5.2.6Free Body Diagrams - Calculations
5.2.7Stretching a Spring
5.2.8Hooke's Law
5.2.9Hooke's Law - Calculations
5.2.10Elastic Potential Energy
5.2.11Elastic Potential - Calculations
5.2.12Exam-Style Questions - Elastic Potential Energy
5.3Effects of Forces
6Waves
6.1Wave Basics
6.2Waves at a Boundary
6.3Sound Waves
6.4Electromagnetic Waves
7Magnetism
7.1Magnetism Basics
7.2Electromagnetism
Jump to other topics
1Energy
1.1Energy Changes
1.1.1Energy Stores
1.1.2Calculating Changes in Energy
1.1.3Changes in Kinetic Energy - Calculations
1.1.4Changes in GPE - Calculations
1.1.5Changes in EPE - Calculations
1.1.6Energy Transfers
1.1.7Mechanical Work Done
1.1.8Mechanical Work - Calculations
1.1.9Electrical Work Done
1.1.10Electrical Work Done- Calculations
1.2Energy Losses & Efficiency
2Electricity
2.1Electric Charge
2.2Resistance & Electrical Work
2.3Electric Circuits
2.4Electricity in Homes
2.5Static Electricity
3Particle Model of Matter
3.1States of Matter
3.2Heat
4Atoms & Radiation
4.1Atoms
4.2Radiation
4.2.1Radioactive Decay
4.2.2Radioactive Decay 2
4.2.3Types of Radioactive Emission
4.2.4Fission & Fusion
4.2.5Radioactive Decay Equations
4.2.6Radio. decay equations - Calculations
4.2.7Half Lives & Ionising Radiation
4.2.8Half Life - Calculations
4.2.9Uses & Dangers of Radiation
4.2.10Uses & Dangers of Radiation 2
4.2.11End of Topic Test - Atoms & Radiation
4.2.12Grade 9 - Radiation
4.2.13Exam-Style Questions - Radioactive Decay
5Forces
5.1Basics of Motion
5.2Forces
5.2.1Gravity
5.2.2Gravity - Calculations
5.2.3Resultant Forces
5.2.4Newton Second Law - Calculations
5.2.5Force Diagrams
5.2.6Free Body Diagrams - Calculations
5.2.7Stretching a Spring
5.2.8Hooke's Law
5.2.9Hooke's Law - Calculations
5.2.10Elastic Potential Energy
5.2.11Elastic Potential - Calculations
5.2.12Exam-Style Questions - Elastic Potential Energy
5.3Effects of Forces
6Waves
6.1Wave Basics
6.2Waves at a Boundary
6.3Sound Waves
6.4Electromagnetic Waves
7Magnetism
7.1Magnetism Basics
7.2Electromagnetism
Unlock your full potential with GoStudent tutoring
Affordable 1:1 tutoring from the comfort of your home
Tutors are matched to your specific learning needs
30+ school subjects covered