atomic structure Flashcards
radius of an atom
1 x 10^-10 m
how much smaller is the radius of a nucleus
10,000
further away the electrons from nucleus..
the higher the energy of electrons
gravitational potential energy
electrons absorbing EM radiation
(electromagnetic)- light, heat
move up higher energy shells
emitting EM radiation
(electromagnetic radiation)- moving up level= unstable
therefore
goes back down energy level to original- emitting wave of em radiation (light waves- colours)
dalton
1800
tiny spheres that cannot be divided
jj thompson
1897
plum pudding
overal charge- neutral
Positively charged mass with electrons embedded
rutherford experiement
1911
alpha particles fired at thin gold foil
- most went through= atom mostly empty space
- some slightly deflected= charged centre
- few deflected by >90= central mass
rutherford
1913
nuclear model
positive nucleus, with cloud of electrons around
bohr
1913
energy shells
chadwick
1932
neutrons
what is radioactive decay?
unstable nuclei emitting radiation (particles/waves) to become more stable- loosing energy
random process- why we cant know when nucleus will decay
activity & unit & how is it detected
rate at which the unstable nuclei from a source of radiation decays
Becquerels (Bq)- 1 nucelus decay/second
Geiger- Muller Tuve
aplha particles
helium nucleus- 2 protons 2 neutrons (NO ELECTRONS)- +2 charge
low penetration- PAPER
high ionisation
few cm
beta particles
fast-moving electrons -1 charge
medium penetration- ALUMINIUM
medium ionisiation
few 10cms
gamma rays
electromagnetic rays
have highest energy out of ^
NO charge
high penetration- LEAD
low ionisation
infinite
half-life
time taken for activity to decrease to half its original value
(ONCE)
calculating radioactive decay
determine how many half lives
raise 1/2 to ^
ratio it correctly
how to protect from irradiation and contamination
irradiation- lead clothing
contamination- radiation suit
where does background radiation come from- natural & man-made
natural- rocks, cosmic rays from space, foods
man-made- exposure to medical testing, fallout from nuclear incidents
sieverts
counts per second
measure of received dose of radiation
rate which radiation hits specific location
medical uses of radiation
medical tracers- gamma emitting isotopes in body
radiotherapy- beams of gamma rays directed at cancer cells
sterilising medical treatment- gamma radiation
risk of using radiation
- kill/damage living cells
- cause cancer
- cause mutations
nuclear fission
splitting of large unstable nucleus into 2 smaller nuclei
1 neutron->2 or 3 neutrons
URANIUM PLUTONIUM
energy
