radioactivity

plum pudding model

atomic model made by jj thomson - atoms were spheres of positive charge with tiny negative electrons stuck in them like fruit in a plum pudding

nuclear model

atomic model discovered by rutherford - alpha particles went through gold foil and some were deflected, most of atoms mass was concentrated at the centre in a nucleus and the nucleus must have a positive charge

bohr model

niels bohr - electrons are in fixed orbits at a set distance (shells)

ionising radiation

any radiation that can knock electrons from atoms

ions

when a particle loses or gains electrons

anion

negative electrons - atom gains an electron

cation

positive electrons - atom loses an electron

isotopes

atoms of an element with the same number of protons but different numbers of neutrons

alpha radiation

alpha particle is emitted from the nucleus

alpha particle

two neurons and two protons (helium nucleus)

beta particles

electrons or positrons

beta minus particle

fast moving electron released by the nucleus

no mass and charge of -1

beta plus particle

fast moving positron

no mass and charge of +1

gamma rays

electromagnetic waves with a short wavelength

ionisation : most to least

alpha radiation, beta radiation, gamma radiation

penetrative : most to least

gamma radiation, beta radiation, alpha radiation

air range : most to least

gamma radiation, beta radiation, alpha radiation

radioactive decay

unstable isotopes tend to decay into other elements and give out radiation as they try to become more stable

alpha decay

mass number decreases by 4

atomic number decreases by 2

beta minus decay

mass number stays the same

atomic number increases by 1

positron emission

mass number stays the same

atomic number deceases by 1

gamma rays decay

mass number stays the same

atomic number stays the same

half life

average time it takes for half the radioactive nuclei in an isotope to decay

background radiation

low-level radiation that is always around us

irradiation

exposure to radiation

radioactive contamination

unwanted radioactive atoms on an object

household fire alarms use alpha particles

• alpha radiation source is placed in a smoke detector

• source causes ionisation and a current of charged particles flows

• in case of fire, the smoke will absorb the charged particles

• current stops and the alarm sounds

sterilisation of food / equipment using gamma rays

• food is irradiated with a high dose of gamma rays that kill all microbes

• medical equipment can be sterilised using gamma rays

• irradiation is a good sterilisation method as it doesnt involve high temperatures so theres no damage to food or equipment

radiation in tracers and thickness gauges

• medical tracer is injected into a patient and is followed using an external detector

• must be beta or gamma emitters so radiation is able to pass out of body before causing too much damage

• gamma tracers can detect leaks in underground pipes

• beta radiation can be used in thickness control

nuclear reactions

• nuclear fusion

• nuclear fission

nuclear fission

nuclear fission is a type of nuclear reaction that releases energy through the splitting of nuclei

nuclear fusion

nuclear fusion is a type of nuclear reaction that releases energy through the joining of nuclei