Topic 6- Radioactivity Flashcards
How much larger is the nucleus radius than the nucleus?
10,000
Where is the mass of an atom
In its nucleus
What is the size of an atom vs a molecule
- 10^-10m
-10^-9 m
What is the atomic number?
Mass of protons
What is the nucleon number?
Mass of neutrons and protons
What is an isotope?
- Same electrons and protons
- Different number of neutrons
- Different mass
What is the relative mass and charge of an electron?
1/2000 (1/1836)
negative
What is the relative mass and charge of a neautron?
- 1
- neutral
What is the relative mass and charge of a proton?
-1
-positive
What is the relative mass and charge of a positron?
-1/2000 (1/1836)
- Positive
What happens to electron orbit when they absorb emissions of electromagnetic radiation?
- Gains energy and becomes excited
- Moves up an energy level, to the next ring (to an unoccupied space)
- Looses energy (form of radiation) and moves back to its ground state
Alpha decay: what happens
- Random unstable nucleus DECAYS/splits into a new less unstable nucleus
- and a Helium nucleus (2 protons and 2 neutrons)
Beta minus decay: what happens
- Unstable isotopes with too many neutrons
- Neutron decays into a proton and electron
- High speed electron cuasing radiation
Beta plus decay: what happens
- Unstable isotopes with too many neutrons
- Positron decays into a neutron and electron
- High speed positron causing radiation
Gamma radiation: what happens
-After alpha or beta decay
- New nucleus is still unstable
- Emits energy as gamma waves
What type of radiation is alpha, beta and gamma?
- ionising radiation
What stops alpha radiation?
- Thin sheet of paper
What stops beta radiation?
- Aluminium (5mm)
- Lead (2-3mm)
What stops gamma radiation?
- Thick lead
- Concreate (1m)
highest to lowest ionising radiation order?
- Alpha
- Beta
- Gamma
What are the natural sources of background radiation?
- Randon gas- decay of uranium and thorium (igneous rocks)
- Internal radiation- Absorb radioactive material (carbon 14 instead of carbon 12)
Artificial sources of background radiation
- Leakages/ accidents of electricity generators that use nuclear energy
- Fall-out with weapons testing
- Accounts for very small percentage
What is background radiation?
Low level radiation present everywhere
What is used to measuring/detecting radiation?
- Photographic film
- Geiger tube and counter
How does the photographic film detect radiation?
- film that changes colour due to radiation
- Mediums placed in front of film to determine the penetrating strength of the (therefore which) radiation
- Open window, paper, lead, concrete
How does the GM detect radiation?
-ionising radiation ionises the gas in the tube
-Free electrons are attracted to the anode
- Their flow creates a circuit
-This produces a clicking sound
How to work out the activity rate of a radioactive substance?
- Count/ time
What is half life?
- The time taken for half the radioactive matter
- Or the Activity rate
- to decrease by half
How do we measure half life using a graph?
- Find the half life
- Fine the time it took
- Repeat with the quatre life
- Find the difference between the two
What is the unit of activity rate of an isotope?
- A becquerel
What was the plum pudding model
- Plum pudding, electrons and protons incased in a nucleus
What was the alpha particle scattering experiment and what where the results?
- Alpha particle shot at thin gold foil
- Most went through
- Some were deflected
- Very few where deflected backwards
What did the fact that most alpha particles went straight through the gold foil prove?
- Most of an atom is just empty space
(positive helium nucleus hit nothing most of the time)
What did the fact that some alpha particles deflected slightly/ backwards through the gold foil prove?
- Nucleus is positive
- The positive helium nucleus was repelled by the larger positive nucleus and changed direction
Why was gold foil used in the particle scattering experiment?
- Highly positive
- Electrons in the gold weren’t attracted to the alpha particle
What was Bohr’s atomic model?
- Quantised electron shells
- Electrons orbit a positive (much larger) nucleus
How is alpha radiation deflected in a magnet?
- Positive movement causes a current
(FBI) force pushes it upwards or downwards - Slightly changes movements
How is beta minus radiation deflected in a magnet?
- Deflected more as it has a smaller mass
- Negative movement causes current in the opposite direction (FBI)
How is beta plus radiation deflected in a magnet?
- Deflected more as it has a smaller mass
- Positive movement causes current in the direction (FBI)
