Radioactivity

travels up to 10cm in air
stopped by paper and skin
high ionising power
mass of 4
charge of +2
structure of 2 protons and 2 neutrons (helium nucleus)

travels up to 1m in air
stopped by a few cm of aluminium or water
moderate ionising power
mass of 0
charge of -1
structure of an electron

travels unlimited distance in air
stopped by several cm of lead or 1m of concrete
very weak ionising power
mass of 0
charge of 0
structure of an EM wave

travels unlimited distance in air
stopped by several cm of lead or 1m of concrete
high ionising power (high KE)
mass of 1
charge of 0
structure of a neutron

Nuclei of unstable isotopes break down at random
The nucleus often changes into a new element

Parent nucleus splits into alpha particle and daughter nucleus
alpha particle is represented as a (with 4 mass number and 2 proton number)

a neutron in the nucleus turns into a proton
releases an electron which is a beta particle

unstable nucleus decays to become a gamma photon and a stable nucleus
gamma decay often happens after another radioactive decay

Particle traveling at high speed at high KE which means that they can cause damage

radon gas from the air
rocks
human body and food
cosmic rays
artificial sources (medical, nuclear power and weapons tests)

Place Geiger counter away from any sources
Count for a specific measure of time (e.g. 1 hour)
Subtract background activity from any measurements

Point away from people
Handle with tongs
Wear a monitor to keep track of exposure

When ionising radiation passes through an object
Occurs when an object is exposed to a source of radiation outside the object
Doesn't cause the object to become radioactive
Stops as soon as the source is removed

Occurs if the radioactive source is on or in the object
A contaminated object will be radioactive as long as the source is on it or in it
Once the object is contaminated, the radiation cannot be blocked from the object

Used to monitor the thickness of paper as it is made in a paper mill (beta)
Used in smoke detectors (alpha)
Used to sterilise medical instruments (gamma)

Radioactive decay is random
We can know the probability that a nucleus will decay in a given second but not which atom in the nucleus
Activity is measured in decays per second (bequerel)
Half-life is the time taken for half of the radioactive atoms present now present in a nucleus to decay

Can damage the DNA in the cells of a living organsim so the cell can either die or mutate (which leads to cancer)

Splitting up of large and unstable nuclei into smaller nuclei
Occurs either spontaneously (which is very rare) or by the atom absorbing a neutron (which can split a nucleus)
Happens in nuclear reactors where control rods are lowered into the reactor to absorb neutrons (as the rate of fission has to be carefully controlled)
Leads to a chain reaction as one fission leads to another fision
Energy from fission is used to heat up water and turn it into steam which is used to drive turbines and power electricity generators

Uranium or plutonium fuel is relatively cheap and produces large and steady amounts of energy
No emissions or pollution as it does not produce greenhouse gases

Very expensive to build nuclear power stations
Risk of disaster
Expensive to get rid of nuclear waste

Two light nuclei fuse together to form a heavier nucleus
Process that fuels stars and is how all elements heavier than hydrogen were made
A small amount of the mass is converted in to huge amounts of energy

No radioactive waste
Easy to make the hydrogen that is needed as fuel

Only happens at really high temperatures and pressures
Is not possible to do it on Earth

Gas under pressure is circulated through the reactor vessel to cool the fuel rods
Hot gas is then passed through a heat exchanger, where water is turned to steam
This steam is then used to drive generator turbines and create electrical power
Cool gas is returned to the reactor vessel