Atomic Theory 4 - Radioactivity

who discovered radioactivity

Becquerel

what did the Curies discover

polonium & radium

radioactivity

spontaneous disintegration of the nucleus with the emission of alpha beta gamma radiation

properties of alpha particles

positive particles

two protons two neutrons (same as helium nucleus)

not very penetrating

example of alpha emitter

americium-241

used in smoke detectors

formula if alpha particle is lost

subtract 2 from atomic number

subtract 4 from mass number

properties of beta particles

negatively charged particles

high-speed electrons

moderately penetrating

example of beta particles

carbon-14

used in carbon dating

what happens when beta particle is emitted

neutron changes into a proton and an electron

formula if beta particle is lost

add 1 atomic number

mass number the same

properties of gamma rays

neutrally charged

high-energy electro-magnetic radiation

extremely pentrating

example of gamma rays

cobalt-60

difference between nuclear and chemical reaction

change in the nucleus & a new element is usually created

electrons being shared or transferred

half life

time taken for half the nuclei in a given sized sample to decay

radioisotope

an isotope of an element that undergoes radioactive decay

uses of radioisotopes

archaeological uses (carbon dating)

carbon dating

the ratio of carbon-12 to carbon-14 remains constant when the organism is alive

when a animal/plant dies the carbon-14 in the plant/animal continues continues to decay very slowly therefore the ratio changes in the organism

by measuring the ratio of carbon-12 to carbon-14 and knowing the half life of carbon-14 the time of death of organism can be calculated

nuclear fission

splitting the nucleus into two roughly equal fragments

nuclear fusion

joining of two smaller nuclei to form a larger one