7b) Radioactivity

Structure of Atoms:

The nucleus of an atom contains protons and neutrons. It makes up most of the mass of an atom, but virtually no space - tiny. in a nucleus are called the atomic number or proton number. The total
The electrons are negatively charged and are small. They are outside of the atom and take up the most space, giving it's overall size. 
The number of protons in a nucleus are called the atomic number or proton number. The total number of protons and neutrons in the nucleus are called the mass number or nucleon number.

Isotopes:
Have the same number of protons, but different number of neutrons (mass number/nuclear number)

Alpha Particles:

• made of 2 protons and 2 neutrons (like Helium) and are big, heavy and slow moving 
• don't penetrate far (easily stopped) 
• Strongly ionising 
• Electrically charged --> deflected by electric and magnetic fields
• emitting alpha particles decreases the atomic number by 2 and the mass number by 4 

Beta Particles

• Electron emitted from the nucleus of an atom when a neutron turns into a proton and an electron. When a beta particle is emitted the number of protons increases by 1, so the atomic number increases too
• Move quite fast and are small 
• penetrate moderately, and moderately ionising 
• Charged --> deflected by electric and magnetic fields 

Gamma rays

• no mass, just energy
• penetrate along way 
• weakly ionising 
• no charge and so isn't deflected 
• gamma emissions happen after alpha or beta decay --> no effect on atomic or mass number 

Penetrating power

Alpha --> blocked by paper, skin or a few cm of air 

Beta --> stopped by thin metal

Gamma --> thick lead or concrete 

Complete balanced nuclear equations:

Alpha decay

Beta decay

How to detect ionising radiation:

• radiation imprints on camera film 
• Geiger-Muller detector (GM counter) beeps in the presence, the more radiation the more frequency it beeps 

Where is it from?

Half Life:

• time taken for half of the radioactive atoms now present to decay 
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Uses and Dangers:
Alpha
detect a fire - ionises air, small current when smoke enters --> alarm goes off
Change cells - don't cause harm outside body, but most inside 

Beta
testing thickness - intensity proportional to paper thickness 
leaks in pipes - put in use GM counter
Change cell - can penetrate deeper into the body, not ionising 

Gamma
detect cracks - like an X ray 
Sterilisation - go through packaged source 
Medical imaging - inject radioactive tracer 
Radiotherapy - kill cancer cells 
Change cells - passed through flesh, bones absorb gamma rays (most) and not very ionising