Radioactivity Flashcards
what was john daltons model of the atom?
1803
Said all matter made from tiny particles called atoms
Said that atoms cannot be divided
what was jj thompsons model of the atom?
1897
‘Plum pudding model’
Atom is ball of positive charge with electrons embedded
DISCOVERED ELECTRON
what was earnest rutherfords model of the atom?
1905
Gold foil experiment
Directed a beam of ‘alpha particles’ at a very thin gold leaf suspended in a vacuum.
Most alpha particles went straight through
Some went bounced off at angles
Atom is mostly empty space
Positive charge must be in very small part of atom
DISCOVERED NUCLEUS
what was neils bohrs model of the atom?
1913
Suggested that the electrons orbited the nucleus in different energy levels or at specific distances from the nucleus
DISCOVERED ELECTRON SHELLS
what was james chadwicks model of the atom?
1932
Said that nucleus must contain neutral particle to add up to mass
DISCOVERED NEUTRON
what are isotopes?
A different form of the same element atoms with the same number of protons but diffrent number of neutrons.
what is radioactive decay?
when unstable isotopes decay into other elemnts and give out radiation as they try to become more stable.
what do radioactiuve substances spit out?
ionising radiation from thore nucleus
what can radioactive substabces also release when they decay?
neutrons
what is ironising radiation?
radiation that knocks electrons off atoms creating positive ions,
the ionising power of a radiation source is how easily it can do this
what is alpha radiation?
when an alpha particle is emmited from the nucleus.
what is an alpha particle?
2 neutrons and 2 protons like a helium nucleus
what can alpha particles be absorbed by?
a sheet of paper
what are the alpha radiation appliances in the home?
smoke detectors - it ironises air particles, using a current to flow, if there is smoke in the air, it binds to the ions meaning the current stops and the alarm sounds
what is a beta particle?
a fast moving electron released by the nucleus.
what are beta paricles absorbed by?
a sheet of alliminium
for every beta particle emitted ……
a neutron in the nucleus has turned into a proton
what are beta emmitters used for?
to test the thinkness of sheets of metal, as the particles are not immediatley absporbed by the material like alpha radiation would be and do not penetrate as far as gamma rays. therefore slight variations in thickness affect the amount of radiation passing through the sheet.
what are gamma rays?
waves of electromagnetic radiation realeased by the nucleus.
why are gamma rays weakly ironising?
theytend to pass through rather than collide with atoms. eventually they hit something and do damage
what can gamma rays be absprbed by?
thick sheets of lead or meters of concrete.
what are the uses o gamma rays?
fibre optic cable use visible light to transmit data
ultraviolet radiation gives you a suntan
used in medicine ( x rays)
what is the charge of apla particles?
+2
what is the charge of beta particles?
+1
what is the charge of gamma particles?
none
what is the mass of apla particles?
4
what is the mass of beta particles?
none
what is the mass of gamma particles?
none
what is the penitration ability of aplpa particles?
least penitration ability
what is the penitration ability of beta particles?
middle penitrating ability
what is the penitration ability of gamma particles?
most penitrating ability
what is the range in air of apha particles?
not much
what is the range in air of beta particles?
more than alpha less than gamma
what is the range in air of gamma particles?
lots of range
what is the ironising ability of alpha particles?
most ironising
what is the ironising ability of beta particles?
middle ironing
what is the ironising ability of gamma particles?
least ironsing
how is unstable nuclei decay measured
using a half life
what can half life be used to predict
radioactive sources, even though thier decays are random
a radioactive source ……….. over time
decreaces
what is half life?
the time taken for the number of radioactive nuclei in a isotope to halve
the initial activity of a smaple is 640 Bq caluclute the final activty after 2 half lives
640 divided by 2 = 320
320 dvided by 2 = 160
(160 divived by 640) x 100 = 0.25
0.25 x 100 = 25%
25%
what is a danger to using radiation?
ironising radiation can enter living cells and ionise atoms within them. this can damage the cells wich can cause cancer or kill the cells completeley.
what is exposure to radiation called?
irradiation
what are ways of reducing irradiation?
keeping sources in lead-lined boxes
standing behind barriers or being in a diffrent room
using remote controlled arms
what is contamination?
contamination is radioactive particles getting into objects
what is said to be contaminated?
if unwated radioactive atoms getting into on onto ann object
what is an example of contamination?
touching a radioactive source without wearing gloves, your hands would be contaminated
what may happen to contaminating atoms?
they might decay and release radiation, which could cause you harm
why is contamination espesically dangerous?
radioactive particles could get inside your body
what sould be done when handilng soucrses to stay safe?
golve and tongs to avoid particles getting stuck or under your nails.
what do some industrial workers wear?
protective suits to stop them breathing in paticles
outside the body beta and gamma sources are the most dangerous, why?
beta and gamma can penetrate the body and get in to delicate organs
why is alpha less dangerous to the body?
it cant penetrate the skin and is easily blocked by a small air gap
inside the body, alpha sources are most dangerous, why?
because they do all thier damage in a very localised area.
beta soucres are less damaging inside the body, why?
radiation is absorbed over a wider area and some passes out of the body all together
why are gamma souces the least dangerous inside the body?
they mostly pass stright out, they have the lowest ironising power
what is an example of a detector for radiation?
a Geiger-Muller tube/counter
