Radioactivity

isotope

same number of protons different number of neutrons

radioactive decay

spontaneous transformation of an unstable nucleus into a more stable nucleus

proton charge

+1

proton mass

1

neutron mass

1

neutron charge

0

electron mass

1/1800

electron charge

-1

gamma radiation

weakly ionising, high penetration stopped by lead

alpha radiation

highly ionising, low penetration, stopped by paper or skin

beta radiation

moderately penetrating and ionising, stopped by aluminium

uses for alpha radiation

smoke alarm

how does smoke alarm work with radiation

alpha particles create current in alarm

smoke enter, particles absorbed

current drips trigger alarm

gamma radiation uses

sterilisation and tracers

beta radiation uses

thickness monitoring

thicker = more particles absorbed

background radiation

weak radiation detected from external sources

eg of background radiation

rocks, cosmic rays, food&drink, medical sources, nuclear waste

half life

time taken for half the time of undecayed nuclei to decay

activity

number if decays per unit bequerels

contaimination

unwanted presence of materials contain radioactive atoms

irradation

exposure of object to radiation

geiger muller to detect radiation

detects count rate of radioactive particles per second

geiger muller method

leave tube in empty room

take reading after 100s

subtract background radiation

fission

splitting a nucleus that releases energy

fusion

two nuclei collide and fuse to create larger heavier nucleus

two hydrogen to from helium

how do stars release energy

nuclear fusion

nuclear fusion conditions

high temp and pressure

due to electrostatic repulsion of protons

nuclear radiation

controls rate of reaction

absorbs neutrons

control rode

(boron) absorb neutrons

coolant

prevents overheating

moderator

slows down neutrons collisions

has a graphite core

core

steel vessel

withstands pressure

absorbs some radiation