1. Atomic Structure
Scale of the Universe

2. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

3. Aristotle 384 -322 BC Describe the plum pudding model
Proposed that all matter is made of five elements:
Fire (hot and dry)
Earth (cold and dry)
Air (hot and wet)
Water (cold and wet)
Aether (divine substance that makes up the heavenly spheres and heavenly bodies (stars & planets)
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

4. Matter composed of tiny indivisible particles.
Demokritos BC
Matter composed of tiny indivisible particles.
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

5. John Dalton 1766-1844 Describe the plum pudding model
All matter is made of atoms, and atoms are indestructible and cannot be broken down into pieces
All the atoms of a particular element are identical to each other and different from the atoms of other elements
Atoms are rearranged in a chemical reaction
Compounds are formed when two or more different kinds of atoms join together
Atoms cannot be divided into smaller particles – they are indivisible.
There are spaces between atoms.
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

6. J.J. Thomson 1856-1940 Development of the plum pudding model
Electrons (like negative ‘plums’) embedded in a ‘pudding’ of positive matter, with the negative charge of the electrons balanced by the positive charge of the ‘pudding’
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

7. The Plum Pudding Model Describe the plum pudding model
Atoms are neutral so are made of equal positive and negative material.
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

8. Gold Foil Experiment
Alpha particles (which are small positive particles) are fired at a gold leaf 𝛼
The gold leaf is surrounded by a detector
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

9. Gold Foil Experiment Geiger and Marsden Rutherford
If the gold atoms are like a plum pudding then all the particles would pass straight through it like a bullet through sponge
Geiger and Marsden
Rutherford
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

10. Gold Foil Experiment Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

11. Results 1. Most particles when straight through the gold foil
2. A small number were bounced straight back at the detector
3. Some of the particles were deflected at large angles
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

12. Structure of the Atom
1. Most particles went straight through the gold foil
Most of the atom is made of empty space
2. A small number were bounced straight back at the detector
The mass of an atom is mostly concentrated in the centre in a dense nucleus
3. Some of the particles were deflected at large angles
The centre mass is positively charged and repels the alpha particles when they pass nearby
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

13. Atomic Structure
This was completely unexpected and meant that the current theory of atomic structure was wrong.
“It was quite the most incredible event that ever happened in my life. It was as if you fired a 15 inch shell at a piece of tissue paper and it came back and hit you.”
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

14. Atomic Structure Positive nucleus (most of the mass of the atom)
Negative part of the atom
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

15. James Chadwick 1891-1974 Discovered the neutron in the nucleus
Neutron – subatomic particle. Same mass as a proton but zero charge.
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

16. Niels Bohr 1885-1962 Electrons circle the nucleus at high speed
Electrons are kept in certain energy levels in a stable formation around the atomic nucleus.
Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

17. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

18. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

19. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

20. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

21. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

22. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom

23. Atomic Structure Describe the plum pudding model
Describe and explain the results of the gold leaf experiment
Describe the structure of the atom