P4 atomic structure Flashcards
what is the radius of an atom
1 * 10^-10
what is an isotope
atom with different number of neutrons
what is EM radiation
when electrons change orbit (closer or further away)
-closer to nucleus emits more radiation
-further absorbs radiation
what did Dalton think about the atom
everything was made of tiny spheres that could not be divided
what did J.J Thomson think about the atom
plum pudding model was found which said the overall charge of an atom is neutral and the negative electrons were scattered on the positive body
what did Rutherford think of the atom
positive nucleus in the centre and negative electrons in a cloud around it
what is the gold foil experiment
alpha particles shot through
-most went straight through
-some slightly deflected
-few were deflected by more than 90 degrees
who perfected the final model of the atom
Bohr
what is radioactive decay
the act of atoms nuclei becoming unstable
what is activity
the rate at which a nuclei decays
what is count rate
number of decays recorded by a counter per second
what are some features of alpha radiation
-helium nucleus
-highly ionising
-weakly penetrating
-causes mass and charge of the nucleus to decay
what are some features of beta radiation
-medium ionising
-electrons
-medium penetration
-causes charge of nucleus to change
what are some features of gamma radiation
-low ionising
-highly penetration
what is half life
time taken for half the nuclei in an atom to decay
what are some features of a short half life
-less of a risk
-initially radioactive but dies down
-less long term risk
what are some features of a long half life
-remains weakly radioactive
-can be used as a smoke alarm because it doesn’t need to be replenished and cant harm anyone
what is contamination
making direct contact with a radioactive object
what is irridiation
radioactive waves reaching an object
what causes background radiation
-cosmic rays
-nuclear fallout
-medical rays
how is radiation used in tracers
-technetium has a half life of six hours so decays into a safe isotope that can be excreted by the body
-injected/swallowed by the body and has enough time to flow through and be detected before it decays away
-gamma emitter so can pass through body tissue and doesn’t cause harm
how is radiation used for chemotherapy
-gamma emitters emit gamma rays near the cancerous parts of the body absorbing the energy and dying controlling the disease
-not very accurate so may kill healthy cells too
what is nuclear fission
the splitting of a large unstable nucleus
explain how nuclear fission works
-unstable nucleus absorbs an extra neutron
-splits into 2 nuclei emitting 2-3 neutrons and gamma rays
-these neutrons may collide with other atoms making them unstable creating a chain reaction
