2.5 Radioactive Substances Flashcards
What’s the mass number?
The total number of protons + the total number of neutrons
What’s the atomic number?
The total number of protons
The total number of electrons
What’s an isotope?
An atom that has a different number of neutrons
What’s a radioactive substance?
A substance that gives out radiation from the nuclei of its atoms all the time
What was the plum pudding model?
What did Rutherford and Marsden’s experiment show?
What happened?
- Most alpha particles went straight through gold foil
- Some alpha particles were deflected by the gold foil
What did it show?
- Most of an atom is just nothing
- There’s a positively charged nucleus (the positively charged alpha particle was repelled by the nucleus)
Where does background radiation come from?
- Naturally occuring radioactive isotopes (air, food, rocks)
- Space (mainly the sun)
- Man-made sources (nuclear weapon tests, nuclear accidents, nuclear waste)
What are the properties of alpha radiation?
- 2 neutrons and 2 protons (a helium nucleus)
- Big, heavy and slow
- Don’t penetrate very far, stopped by air
- Strongly ionising
What are the properties of beta radiation?
- An electron
- Quite fast and quite small
- Moderately penetrating
- Moderately ionising
- When a beta particle is emitted, a neutron turns into a proton
What are the properties of gamma radiation?
- Short wavelength electromagnetic waves
- Very penetrating
- Weakly ionising
What happens in terms of mass number and atomic number when an alpha particle is emitted?
Atomic number = Down 2
Mass number = Down 4
What happens in terms of mass number and atomic number when a beta particle is emitted?
Mass number = Stays the same
Atomic number = Up 1
What happens to alpha and beta particles in a magnetic field?
They are reflected in different directions due to their different charges. The alpha particles are deflected with a greater force as they have a greater charge
What is half life?
The average time it takes for the number of nuclei in a radioactive isotope sample to halve
Give some uses of radiation? (4)
- Smoke detectors - alpha
- Tracers in medicine - beta or gamma
- Radiotherapy
- Sterilisation of food and surgical equipment - gamma
What is the most dangerous type of radiation inside the body?
Alpha
What is the most dangerous type of radiation outside the body?
Beta and gamma
Give some safety precautions when using radiation (4)
- Use radioactive substances for as short of a time as possible
- Don’t touch the radioactive substance, hold it at arm’s length with tongs
- Keep the source pointing away from you and don’t look at it directly
- Store it in a lead box, wear lead aprons, stand behind lead screens
