radioactivity

alpha particle

2 protons and 2 neutrons

alpha radiation

most ionising

shortest range through air

stopped by a sheet of paper

beta radiation

less ionising than alpha but more than gamma

longer range through air than alpha but shorter than gamma

stopped by a sheet of aluminium

beta -

an electron

released when a neutron turns into a proton

beta +

a positron

released when a proton turns into a neutron

gamma radiation

least ionising

longest range through air

stopped by a block of lead

radioactive decay

occurs when an unstable nucleus tries to become stable by releasing alpha beta or gamma

initial element

new element + type of radiation

dangers of radiation

radiation ionises cells

could damage dna in the cells

leads to mutation

leads to cancer

half life

time taken for half of the radioactive nuclei in a substance to decay

irradiation

object is exposed to the radiation from outside the body

contamination

object becomes radioactive itself

nuclear fission

a nucleus splits into 2 smaller daughter nuclei

when this happens energy is released

control rods

moveable rods that can absorb neutrons to control the rate of fusion

moderators

used to slow down neutrons so the uranium rods can capture them

this increases the rate of fission

nuclear fusion

a process where 2 small nuclei join together to form one big nucleus

some of the mass is coverted to energy

two conditions for nuclear fusion to occur

extremely high temperatures

extremely high pressures

rutherfords gold foil experiment

gave evidence for the nuclear model

rutherfords - most of the alpha particles went through

most of the atom must be empty space

rutherfords - some of the alpha particles were detected at slight angles and very few at angles reater than 90

there is concentrated mass in the centre of the atom - the nucleus

background radiation

radiation that is always present in a particular area

radon rocks

releases radon gas which is highly ionising

geiger muller tube

measures radioactivity

countrate

measurement of how radioactive an object is