p7 atomic physics

what is the structure of an atom according to the nuclear model

a small dense nucleus in the center with all the mass surrounded by empty space with orbiting electrons

what is the actual charge of a proton/electron

-/1.6 × 10^(-19) coulombs

how does alpha scattering prove the nuclear model

since when a beam of alpha particles is fired at thin metal foil a lot of the particles go through it shows that there is empty space in between the nuclei that deflect the particles

what is a nuclide

a distinct ‘species’ of atom with an exact number of protons and neutrons and a specific nuclear energy state.

what are isotopes

2 or more nuclides that share the same number of protons but different number of neutrons

what is the nucleon number

the number of protons + neutrons in an atom

how do you find the relative mass/charge of an nuclide

for the relative mass you add up the number of protons and neutrons. for the charge you subtract the number of

what is radioactive decay

a random process where unstable nuclei release ionizing radiation in order to become more stable

how is alpha radiation created

sometimes when a nuclear isotope is unstable it shoots out a helium nucleus(2 protons 2 neutrons) to transform into a lighter element and become more stable.

what are the properties of alpha radiation

alpha radiation is very ionizing but isnt very penetrating, could be stopped by a piece of paper. it travels a few centimeters in air

how is beta radiation released

a neutron decays into a proton and a high speed electron that gets ejected out of the nucleus to make a different more stable element

what are the properties of beta radiation

is it moderately penetrating and ionizing, it can be stopped by 3-5mm of aluminium. it travels a few meters through air

how is gamma radiation released

when releasing alpha or beta radiation the nucleus is often left in a high energy state and the excess energy is released through high frequency electromagnetic waves.

what are the properties of gamma radiation

gamma radiation is very penetrating since it is an electromagnetic wave but it is not very ionizing. in needs to be stopped by roughly 40 cm of lead. it travels for long distances through air

what does the ionizing power of radiation depend on

the charge since radiation can ‘rip out’ electrons from an atom if it has a charge, and kinetic energy since it can transfer more energy to the atom and therefore is more likely to ionize it.

what is the formula for alpha decay of uranium 238

the alpha particle can also be written as ‘He’ since its a helium nucleus

how do you draw the beta decay of carbon 14

the beta particle can also be written as ‘e’ since its an electron

why do nuclei experience nuclear decay

nuclei are unstable if they have too much energy, if they have too many neutrons or if they are too heavy, so emit gamma/beta/alpha radiation in order to lose energy/neutrons/mass.

what is the name of the device that detects radioactive particles and how does it work

it is called a geiger-muller counter and it has a tube of has inside of it that gets ionized and sends out a small electric pulse whenever it gets hit by a radioactive particle

what is radiation measured in

counts per minute(CPM), meaning the amount of radioactive particles that are released per minute

how does does each type of radiation interact with a electric field

beta particles will be attracted to the positive plate since they are negative and alpha particles would attract to the positive plate. beta particles deflect more due to having less mass. gamma is uncharged so it is unaffected

how do alpha and beta particles behave in a magnetic field

they change direction is accordance to flemming’s left hand rule, with current being in the direction of travel for alpha and in the opposite direction for beta. alpha gets deflected less due to greater mass

what is nuclear fission

it is a nuclear reaction that is usually artificially stimulated by firing a neutron into an already unstable nucleus causing it to split into 2 different daughter nuclei and release radiation

what is the equation for fission of uranium 235

where does the energy for gamma radiation released in fission come from

some of the mass of the uranium nucleus is lost and turned into energy that is released as gamma radiation and heat

how is electricity generated from fission

the radiation and internal energy generated heat water that boils and spins turbines with generators that generate electricity. neutron are fired into radioactive particles to start the chain reaction

what is nuclear fission

when 2 different helium nuclei fuse to make one larger helium atom, generating energy from lost mass in the process

what are the name for helium 1 helium 2 and helium 3

protium for hydrogen 1, deuterium for hydrogen 2, tritium for hydrogen 3

how do you draw the equation for fusion of protium and deuterium

is fission or fusion more efficient(energy per gram of fuel)

fusion

what kind of process is radioactive emissions

it is a random and spontaneous process that cant be predicted. the direction for emissions is also random

what is a half-life

the period of time needed for half of the substance to decay, for half of the original mass of radioactive substance to remain

what are 5 sources of background radiation

unstable isotopes in air(radon-222), in food(potassium-40, carbon-14), in building materials and rocks under our feet(uranium-238), radiation from the sun(fusion), cosmic rays from space(black holes)

how does background radiation influence the measurement of half life

if manually measuring cpm then then you need to subtract 20 cpm in order to account for background radiation that can cause anomalous results

how are alpha emitters used in smoke detectors

the alpha radiation ionizes the air in the detector and allows current to pass, but once smoke enters the detector it attaches to the air and block current

what is a radioactive tracer and how is it used

a radioactive substance that usually releases gamma radiation(to prevent cell damage and allow for detection since it passes through the body) that gets injected into the body and is used to detect cancers by tracking it using a detector

how does radiotherapy combat cancer

it uses highly concentrated gamma rays to shoot them at the cancer in order to attempt to kill the cells while trying to minimize the amount that hits the rest of the body

why is sterilizing with gamma rays benefitial

if a strong source with a long half life is used it can kill bacteria quickly and doesnt need high temperatures like boiling meaning that it wont damage heat sensitive materials

how are beta emitters used to control thinkness

since a certain thickness would stop beta particles, having a sensor detect beta emissions through a sheet means that the amount of radiation getting through can help determine if thickness is within limits

what does radiation do to cells

it damages cells; weak radiation makes them mutate by ionizing and flipping codes in dna, and it kills them if its strong.

what are 4 safety precautions for minimizing exposure to radiation

spend less time exposed to the source, increase the distance between you and the source, use thick lead shielding to completely absorb radiation, wear gloves or use tongs to avoid physically touching the material