A Quantum Journey

1
A Quantum Journey

• The 20th Century View Of The Atom

2
Atomic Structures Are Developed To Explain
Phenomena
Thomsons Plum Pudding Model Explained
Electricity
3
Rutherfords Atomic Structure
4
Problem With Rutherfords Model
Accelerated charged particles will radiate EM
waves
The electron is in orbit therefore accelerated
It should lose energy and spiral inwards to
nucleus
EM waves
But this doesnt happen!
5
Bohrs Atomic Structure
The electrons can only exist in specific orbitals
or energy levels because energy is not continuous
These energy levels each have a quantum number, n
6
The Electron
You cannot say where an electron will be at any
time
You can only give the probability that it will be
there
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The Electron
You cannot measure both momentum and position at
the same time
This is called Heisenbergs Uncertainty Principle
8
The Proton
Concentrated positive charge in the nucleus
The nucleus should repel and blow apart
But nucleons have a deeper structure
9
The Proton
The proton is made of three quarks
An up quark has a charge of 2/3 and a mass of
(approximately) 1/3
A down quark has a charge of 1/3 and a mass of
(approximately) 1/3
Mass 1/3 1/3 1/3 1
Charge 2/3 2/3 1/3 1
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Colours Of Quarks
Quarks are said to have colours
There are three colours blue, red and green.
The three colours of quark are attracted together
This works by the exchange of gluons, and is
called the strong force
11
Forces In The Atom
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The Neutron
The neutron is also made of three quarks
Mass 1/3 1/3 1/3 1
Charge 2/3 1/3 1/3 0
Protons are stable BUT neutrons can decay
13
Beta Decay In The Neutron
This is an example of the weak force, of which
the W is a boson
14
Conclusion
Model of the atom has greatly changed in the 20th
Century
Thomsons Plum Pudding Model introduced electrons