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Atomic Structure (Developing the model of the atom (What did John Dalton…
Atomic Structure
Developing the model of the atom
What did John Dalton come up with?
The atom
What did JJ Thomson come up with?
Electrons
What did Rutherford come up with?
Rutherford replaced the Plum Pudding Model with the Nuclear model
What did Bohr come up with?
Electrons orbiting the nucleus do so at certain distances (energy levels)
What is the modern structure of the atom?
The Nuclear Model
A positively charged nucleus
Surrounded by negative electrons
Contains a group of positive protons (protons)
Negative electrons orbiting on energy levels
The number of protons = the number of electrons
Background radiation
What is it?
The low-level radiation that is around us all the time
Where does it come from?
Unstable isotopes which are all around us
Air
Food
Rocks
Building Material
What is irradiation?
Exposure to radiation
What is contamination?
Radioactive particles getting onto objects
What does the seriousness of radiation and contamination depend upon?
Outside the body, beta and gamma are the most dangerous
This is because beta and gamma can penetrate the body and get to the delicate organs.
Alpha is less dangerous because it can't penetrate the skin and is easily blocked by a small air gap;
Inside the body, alpha is the most dangerous
They do all their damage in a very localised area.
Because of this, contamination rather than irradiation is most dangerous with Alpha.
Alpha, Beta and Gamma
Properties of alpha
What are there uses?
Smoke alarms
A Helium Nuclei
Very ionising
Stopped by paper
Properties of Beta
What are there uses?
Used to test the thickness of sheets of metal
High speed electrons
Travel a few m's in air
Pass through up to 4mm of aliminium
Properties of Gamma
What are there uses?
Medical tracers
EM Waves with a short wavelength
Travel far in air
What is half life?
Draw a graph of half life
How do you calculate half life?
The amount of time it takes for half the amount of radioactive substance to decay
What is an isotope?
Isotopes are different forms of the same element
Different number of neutrons
Same number of protons
Is decay a random or controlled process?
Random