atomic structure Flashcards
what did john dalton say?
matter was made of tiny spheres, each element made up of a different type of atom
what did JJ Thomson discover?
electrons that could be removed from atoms, atoms were spheres of positive charge with tiny negative electrons. plum pudding model.
what did rutherford discover?
gold foil experiment with alpha particles, most of mass was concentrated at centre in a nucleus, that was positively charged, rest of atom was empty space.
what did neil bohrs say?
electrons orbiting nucleus do it at a certain distance called energy levels.
what did James Chadwick prove?
existance of the neutron, explained imbalance between atomic and mass number.
what makes up most mass of an atom?
the nucleus
what does number of protons =? (atomic number)
number of electrons
what do unstable isotopes tend to do?
decay and realise radiation trying to become more stable
what are alpha particles?
helium nuclei.
whats in alpha particles?
2 neutrons and 2 protons
explain alpha particles?
dont penetrate very far, stopped quickly, absorbed by shet of paper, strongly ionising.
what are beta particles?
high speed electrons
what in an beta particles?
no mass, charge of -1
explain beta particles?
moderately ionising
penetrate moderately
absorbed by sheet of aluminium
what happens everytime a beta particle is emitted?
a neutron in the nucleus is turned into a proton
what are gamma rays?
EM waves with short wavelengths
what are gamma rays made up of?
electromagnetic radiation released by the nucleus
explain gamma rays?
penetrate far into materials, weakly ionising, absorbed by thick sheets of lead
what happens when an alpha particle is emitted?
atomic number reduces by 2
mass number reduces by 4
what happens when a beta particle is emitted?
increase atomic number by 1
mass stays the same
what happens when a gamma ray is emitted?
no chance in atomic mass or atomic number
what can radiation be measured with?
geiger-muller tube and counter.
what can half-life be used to find?
rate that a source decays
whats the problem with trying to measure decay?
activity never reaches 0
what does a short half life mean?
they are dangerous as they release huge amounts of radiation at start.
what does a long half life mean?
releases small amounts of radiation for a long time, (can be dangerous because nearby areas exposed to radiation for millions of years)
what does radiation dose tell us?
risk of harm to the body tissues due to exposure to radiation
where can background radiation be found?
in our food, in rocks, air, building materials.
what does irradiated mean?
exposed to radiation.
how to you reduce irradiation?
keeping sources in lead lined boxes
what does contaminated mean?
unwanted radioactive atoms getting onto an object
what should you use when handling sources?
tongs and gloves, protective suits.
what sources are most dangerous outside the body?
beta and gamma
why are gamma and beta rays dangerous?
they can penetrate body to get to delicate organs
whats most dangerous inside the body?
alpha, most ionising.
what are risks of radiation?
enter living cells and ionise atoms, damage tissue, cause cancer (mutation), kill cells
how are gamma rays used in medical tracers?
pass through body without causing much ionisation, short half life so they disappear, swallowed or injected into people.
what happens during radiotherapy? (treating cancer with radiation)
gamma rays directed at right dosage to kill cancer cells, damage done to normal cells that can cause sickness
risks of using radioactive materials?
can cause cancer
benefits of using radioactive materials?
tracers can diagnose life-threatening conditions, can remove cancer
what happens during nuclear fission?
nucleus absorbs a neutron, atom splits to form 2 lighter elements, 2 or 3 neutrons released, if any are slow enough they could be absorbed by another nucleus so more fission occurs.
what do control rods do?
absorb neutrons in reactors to slow down chain reaction and amount of energy released.
what is nuclear fusion?
2 light nuclei collide and fuse, create larger heavier nucleus, releases lots of energy.
