radioactivity -CH7

radioactive

a substance with an unstable nucleus

isotope

atoms of the same element with same number of protons but a different number of neutrons

alpha decay

mass decreases by 4, atomic number decreases by 2

beta decay

atomic number increases by 1

gamma decay

both stay the same

plum pudding model

a sphere of positive charge with negative electrons in, made by J.J. Thomson

Ernest Rutherford

discovered the nucleus

gold foil experiment

Geiger and Marsden thought alpha particles would go straight through but as some scattered and some bounced straight back they realised there must be a concentrated part in the middle of the nucleus

alpha penetration

stopped by skin or paper

alpha ionisation

strong

beta penetration

0\.5mm aluminium sheet

beta ionisation

medium

gamma penetration

thick lead

gamma ionisation

weak

irradated cells

their chromosomes can’t replicate normally

alexander litvienko

Russian spy who was poinsed with alpha, the murderers were traced as they left small bits of alpha wherever they went

alpha in smoke alarms

when smoke enters alpha is absorbed so less ionisation happens and then less current flows sounding the alarm

beta thickness control for aluminium foil

the correct thickness will allow some beta to get through but not all

gamma in radiotherapy

kills the harmful, cancerous pathogens

half life

time taken for the mass or the isotope in a sample to half

dosimeter

radiation badges that changes colour after too much contact with radiation

nuclear fission

a large nucleus splits into 2 smaller nuclei releasing energy and a couple of neutrons

nuclear fusion

small nuclei fuse to together to form a large nucleus releasing energy

nuclear fission power stations

high energy output, low running costs, but emits ionising radiation

nuclear fusion power stations

high energy output, no radioactive waste, but requires more energy than is made

natural background radiation

rocks, cosmic rays, radon and some foods

artificial background radiation

nuclear medicine, nuclear bombs and nuclear testing

Geiger counter

used to measure the amount of radiation

irradiation

radioactive substances on the outside

contamination

has radioactive substances inside the cell