07 Radioactivity And Particles Flashcards
(68 cards)
Proton relative charge, relative mass and location
Relative charge = +1
Relative mass = 1
Location = nucleus
Neutron relative charge, relative mass and location
Relative charge = 0
Relative mass = 1
Location = nucleus
Electron relative charge, relative mass and location
Relative charge = -1
Relative mass = 1/1835
Location = shells around nucleus
Atomic number
Small number
- number of protons
Mass number
Large number
- protons + neutrons
Number of neutrons =
Mass number - atomic number
Isotope
Elements with same number of protons but different number of neutrons
- so it has different mass number
What happens when a nucleus is unstable
- it tries to become more stable by ejecting mass (beta/alpha) or energy (gamma)
- the atoms are radioactive
- process of ejecting is called decay
Decay is
Random
Alpha radiation
Helium nucleus emitted from nucleus
- 2 protons 2 neutrons
Beta radiation
Electron emitted from nucleus
Gamma radiation
High energy electromagnetic wave
Alpha ionising and penetration
- very ionising
- low penetration (stopped by paper)
Beta ionising and penetration
- moderate ionisation
- moderate penetration (stopped by aluminium)
Gamma ionising and penetration
- not very ionising
- very penetrating (stopped by lead)
Practical: investigate penetration powers of different types of radiation using radioactive sources
- measure background count for 2 mins using Geiger-Muller (GM) tube and stopwatch —> with no radioactive sources present
- set up source 2cm away from GM tube
- record counts detected from source with no absorbing materials for 5 mins
- place paper between ionising radiation source and GM tube and record counts detected for 2 mins
- repeat with aluminium and lead and record counts
Why do you measure count for at least two minutes
To collect avg value since decay of unstable atoms is RANDOM
Alpha effect on mass/atomic number
4
2
Beta effect on mass/atomic number
0
-1
Gamma effect on mass/atomic number
0
0
Neutron effect on mass/atomic number
1
0
How does GM tube detect ionising radiation
- detects when gas in chamber is ionised by radiation
- every beep is one incidence on radiant (could be gamma/beta/alpha)
How does photographic film detect ionising radiation
When radiation comes into contact with photographic film it DARKENS
- shows presence of radiation
Origins of background radiation
Food and drink
Nuclear power
Medical
Radon gas
Cosmic rays