radioactivity Flashcards
order of scientists that discovered more about atoms
- john dalton
- jj thompson
- rutherford
- niels bohr
- james chadwick
what is the plum pudding model
designed by jj thomson
sphere of positive charge with negative electrons studded into it
what is the rutherford scattering
firing alpha particles at thin gold foil, bc the mass of atom should be spread and pass through. but they were deflected meaning most mass was centred in a nucleus with positive charge.
what is the nuclear model
positively charged nucleus in cloud of negative electrons
——>
nucleus of protons that add to overall charge of nucleus, electrons orbiting at certain energy levels
what did james chadwick do and why
discovered neutrons because there was an imbalance between atomic numbers and mass numbers
charges of each subatomic particle
proton +1
neutron 0
electron -1
what is the bottom number on an element
atomic number - number of protons
what is an isotope
atoms with same number of protons but different number of neutrons
what is radioactive decay
when unstable isotopes decay into other elements, they give out radiation as they try to become more stable
what is ionising radiation
radiation that knocks electrons off atoms, making positive ions
what do you say about something that can know electrons off atoms easily
it has a high ionising power
structure of alpha particle and symbol
helium, two protons and two neutrons
a shape
travel distance, ionising strength, and blocking material of alpha radiation
only travel a few cm in air
highly ionising
stopped by sheet of paper
travel distance, ionising strength, and blocking material of beta particles
few metres in air
moderately ionising
stopped by aluminium
travel distance, ionising strength, and blocking material if gamma rays
long distance through air
weakly ionising
stopped by lead or concrete
what do nuclear equations show
how radioactive decay changes an element
what happens when an atom emits an alpha particle
charge and mass DECREASE
atomic number: -2
mass number: -4
(+ [4/2] He)
what happens to charge and mass of an atom when beta decay occurs (in terms of subatomic particles)
charge INCREASES, mass STAYS SAME
atomic number: +1
(+ [0/-1] e)
what is radioactive decay
when unstable nuclei decay into other elements gives out radiation as they become more stable
what is a half life
the time taken for half the unstable nuclei in an isotope to decay
how do you write 1 decay per second
1 becquerel / bq
what is background radiation
the low level radiation that is around us all the time
3 places that background radiation comes from
soil
cosmic rays
nuclear explosions
what is irradiation
when something is exposed to a radioactive source
what is contamination
radioactive particles getting onto objects
which radioactive rays are most dangerous OUTSIDE BODY and why
beta and gamma
they penetrate body to organs
why is alpha radiation so dangerous INSIDE BODY
it cannot penetrate the skin so it is stuck inside
highly ionisiny
how can gamma sources be useful
medical tracers
what is radiotherapy and what are the risks
directing an accurate dosage of gamma rays to kill cancer cells
normal cells can be damaged
nuclear fission vs fusion
fission: splitting large unstable nuvleus
fusion: joining small nuclei
bases of nuclear fission
NATAC
• neutron must be absorbed
• atom splits to form two new lighter elements of roughly same size
• two or three neutrons released in process
• absorbed by other nucleus
• chain reaction
bases of nuclear fusion and example
two light nuclei collide at high speed and join to make larger heavier nucleus
hydrogen nuclei fuse to produce helium nucleus
