P4 atomic structure

1 * 10^-10

atom with different number of neutrons

when electrons change orbit (closer or further away) -closer to nucleus emits more radiation -further absorbs radiation

everything was made of tiny spheres that could not be divided

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

positive nucleus in the centre and negative electrons in a cloud around it

alpha particles shot through -most went straight through -some slightly deflected -few were deflected by more than 90 degrees

Bohr

the act of atoms nuclei becoming unstable

the rate at which a nuclei decays

number of decays recorded by a counter per second

-helium nucleus -highly ionising -weakly penetrating -causes mass and charge of the nucleus to decay

-medium ionising -electrons -medium penetration -causes charge of nucleus to change

-low ionising -highly penetration

time taken for half the nuclei in an atom to decay

-less of a risk -initially radioactive but dies down -less long term risk

-remains weakly radioactive -can be used as a smoke alarm because it doesn’t need to be replenished and cant harm anyone

making direct contact with a radioactive object

radioactive waves reaching an object

-cosmic rays -nuclear fallout -medical rays

-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

-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

the splitting of a large unstable nucleus

-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