1. Key Areas covered
The orders of magnitude – the range of orders of magnitude of length from the very small (sub-nuclear) to the very large (distance to furthest known celestial objects).

2. What we will do today Describe the standard model of the atom
Discuss and define different orders of magnitude from the very small to the very large

3. Particles and Waves
Unit 2

4. The atom

5. The Standard Model of the Atom
Plum pudding model of the atom:
For centuries scientists have investigated what particles everything is made up of. + -
In 1910, Ernest Rutherford set up an experiment:
Rutherford Scattering
Rutherford’s observations:
Most α particles passed through without much deflection.
A few α particles were deflected at a large angle.
Source of α particles
Gold foil α
Rotating detector
vacuum
(a)
(b)

6. The Model of the Atom Model of the Atom: Electrons in orbit−
Negative charge
Rutherford’s conclusions:
The atom was mainly empty space.
At the centre of the atom there was a small, highly dense, positively charged nucleus.
protons
Positive charge +
nucleus
neutrons
no charge

7. The relative masses and charges of the proton, neutron and electron are:
Particle
Mass
Charge
Symbol
Proton 1
+ 1
1 p
Neutron
1 n
electron
1/1840
- 1
0 e -1

8. It is important to understand the scale of sizes scientists have studied…
Powers of Ten film

9. Orders of Magnitude Smaller than a human, eg: Particle or object
Neutrino
Proton
Hydrogen atom
Dust
Human being
Order of magnitude
~10–24 m
10–15m
10–10 m
10–4 m
100 m
Larger than a human, eg:
Particle or object
Earth
Sun
Solar system
Nearest star
Galaxy
Distance to a quasar
Order of magnitude
107m
109m
1013m
1017m
1021m
1026 m

10. Revised Higher 2012 E

11. 2013 Revised Higher

12. Possible answer
Rutherford’s experiment on the atom had two main conclusions:
The atom is mainly made up of empty space
At the centre of the atom there was a small, highly dense, positively charged nucleus.
Therefore this diagram could be considered a good representation of an atom.
The centre point (nucleus) is made up of protons (+ve charge) and neutrons (no charge).
The electrons (-ve) are on the outer shells.
The space between the nucleus and electrons would realistically be much greater.
Electrons are thousands of times smaller than protons and neutrons and therefore the scale is not entirely accurate.