P5 - nuclear physics Flashcards
(42 cards)
define isotope
-atoms of the same element with the same number of protons & electrons but different numbers of neutrons
-most elements have them with 1 or 2 stable ones
-the unstable isotopes decay & emit radiation
similarities & differences between different isotopes
same:
-no. protons
-no. electrons
-charge
different:
-heavier
-diff. mass no.
-no. neutrons
nucleus
-contains the proton & neutron
-where the mass is concentrated
charge of the nucleus
positive because of the proton
atomic number
-proton number
-nuclide notation: Z
mass number
-nucleon number
-nuclide notation: A
nuclide notation
A
element
Z
what is fission & fusion
-fission - large nucleus splits into daughter nuclei; chain reaction eg. nuclear power station
-fusion - 2 small nuclei join into a heavier nucleus eg. stars
-both produce lots of energy
evidence of the atomic structure: Rutherford, Geiger, Mursden
-Alpha particles are sent to an atom
-particles either deflected fully, deflected slightly or bound off from the nucleus
-conclusion: atom is mostly an empty space & most of its mass is concentrated at its nucleus
background radiation
-radiation in the surroundings all the time
define radioactive substance
substance that decays by emitting radiation from its atonic nuclei
2 harmful ways radioactive substances touch us
1) contamination - radioactive substance gets inside the body
2) irradiation - radiation/ radioactive substance hits our bodies
natural sources of radiation
1) radon - radioactive gas that comes from radioactive uranium rocks underground
2) ground & rocks - contains radioactive substances; use materials form the ground to build buildings & houses
3) space - cosmic rays
artificial sources of radiation
medical sources:
1) X rays
2) Gamma rays - to destroy cancer cells
3) medical radiographers
nuclear power stations:
how to detect radiation
-use a Geiger’s counter
-records the rate of radiation (count rate)
-counts per seconds/ minutes
how does Geiger’s counter work
-when radioactive particle enters the tube, it ionizes the gas inside & triggers an electrical discharge with a click sound
-signal is sent to the electronic counter that registers the number of clicks
Geiger’s counter disadvantage
-count rates includes background radiation & the radioactive source
-correct count rate = measured count rate - background count rate
define radioactive decay
-random process when an unstable nucleus gives out
radiation to become more stable
-random process, direction of emission is random
-not affected by external factors eg. temp
when does a nucleus become unstable
1) too many protons
2) too many neutrons
how does radiation ionizing nuclear radiation
-radiation may knock electrons out of atoms
-ions are formed
Alpha particle:
-symbol
-made of
-charge
-in an electric field
-in a magnetic field
-symbol = α
-made of = 2 protons + 2 neutrons (helium)
-charge = +2
-in an electric field = towards the negatively charged plate
-in a magnetic field = Fleming’s left hand rule
range in air = a few cm
Beta particle:
-symbol
-made of
-charge
-in an electric field
-in a magnetic field
-symbol = β
-made of = an electron
-charge = -1
-in an electric field = towards the positively charged plate
-in a magnetic field = Fleming’s left hand rule
range in air = a few 10’s of cm
Gamma rays:
-symbol
-made of
-charge
-in an electric field
-in a magnetic field
-symbol = γ
-made of = electromagnetic radiation
-charge = neutral
-in an electric field = not deflected; uncharged
-in a magnetic field = not moved; uncharged
range in air = infinite
Penetrating power among alpha, beta & gamma
Alpha: weak penetration
-absorbed most easily
-absorbed by a thin sheet of paper
-cannot penetrate skin
Beta:
-easily travels through air/ paper
-absorbed by a few mm of metal eg. aluminum
Gamma: strong penetration
-takes several cm of lead/ concrete to absorb
