nuclear physics- topic 5 Flashcards
describe structure of an atom
divided in 2 parts
1. a nucleus which composed by protons and neutrons
2. negative electrons which orbit the nucleus in shells
how do atoms form positive vs negative ions
positive- lose electrons
negative-they gain electrons
what did the alpha particle scattering experiment prove
(a) a very small nucleus surrounded by mostly empty space
(b) a nucleus containing most of the mass of the atom
(c) a nucleus that is positively charged
how does the alpha particle scattering experiment proves what it does
most alpha particles pass stright through
rarely a few alpha particles are deflected by a few degrees
very rarely an alpha deflect more than 90 degrees
what is relative charge of proton neutron and electron
proton- +1
neutron- 0
electron- -1
what is meant by atomic number
number of protons in a nucleus = number of electrons if atom neutral
what is meant by mass number
nuclean number thus total number of protons and neutrons in a nucleon
how do you calculate number of neutrons in an atom
nucleon number - proton number
explain nuclide notation
mass number is normally above, and is the biggest number
while atomic number is under and smaller
what is meant by an isotope
a nucleus or atom with the same number of protons but with a different number of neutrons, have different densities but same chemical properties
describe nuclear fussion
when 2 light nuclei join together to make a heavier nucleus releasing a huge amount of energy
the mass always decreases, and energy increases due to change of mass into energy
describe nuclear fission
the splitting of a heavy nucleus into two smaller ones
mass decreases as it is converted into mainly kinetic energy as a product, thus releasing a large amount of energy
relationship between proton number and relative charge on a nucleus
proton number is the chrage of the nucleus
relationship between nucleon number and mass of nucleus
nucleon number is number of proton and neutrons added together, thus its mass
difference between atoms and ions
atoms have equal number of protons and electrons, thus are neutral
ions have different number of protons to electrons, and are charged
what is background radiation
radiation detected everywhere, such as cosmic rays, gamma rays from star, radong gas which are found in food, buildings, ourselves
what makes up most of background radiation
radon gas (in the air)
rocks and buildings
food and drink
cosmic rays
how can ionising nuclear radiation be measured
using a detector connected to a
counter
what is count rate measured in
counts/s or
counts/minute
how does an unstable nucleus gain stability
emitting one of 3 types of radioactivity, alpha, beta, gamma
why is a nucleus unstable
because it is too heavy or has too many neutrons, needs to lose them
Describe the emission of radiation from a nucleus
spontaneous and random in direction
what are the types of radioactivity
alpha, beta, gamma
describe alpha particles
-helium nucelus (He)
-relitevly slow
-highly ioninsing (big mass and move slowly, has a large charge)
-charge of 2+
-weakly penetrating ( stopped by paper, travels only a few cm in air)
what happens to alpha radiation in electric fields
moves straight and then bends into negative side, less than beta curved because of its larger mass
what happens to alpha radiation in magnetic fields into paper
moves along the convectional currrent thus moves bends upwards, at constant speed
what is the nuclear notation of helium
4= mass number
2=atomic number
2+=charge
describe alpha decay equation
unstable particle loses 4 in the mass number and 2 in the atomic number
describe beta radiation
-fast moving electrons
-less ionisation than alpha but more than gamma because beta has less mass and ke and charge than alpha but more than gamma
-penetrating abilities mid, pass throguh paper stopped by a few mm of aluminium
describe beta particles in electric fields
move stright until reaches fields then radically curvs towards positive plate
describe beta particles in magnetic fields into paper
moves opposite to convectional current, thus curvs downwards
what do you use to determine the movement of radiation through magnetic fields
flemmings left hand rule
describe beta decay equation
unstable particle simply gains +1 in its atomic number
describe beta particle
electron
mass= 0
charge=-1
what happnes to the neutron of an unstabble particle emmiting beta radiation
it becomes a proton and a electron
describe gamma rays
-no charge or mass
-high frequency electromagnetic transversewaves
-travles in speed of light in a vaccum
-low ionisation (no charge or mass)
-only stopped by severla cm of dense lead
what happens to gamma rays in electric and magnetic fields
nothing because it has no charge
describe equation of gamma decay
same unsable particle + gamma in the product side
what determines the ionising effects of each radiation
its charge
its mass
its relative ke
what happens in alpha and betta decay
nucelus changes to that of a different element
why can isotopes of an element be radioactive
due to an excess of neutrons in the
nucleus and/or the nucleus being too heavy
what is the half life of a particular isotope
the time taken for half the nuclei of that
isotope in any sample to decay
describe the radiation used in smoke detectors or fire alarms
alpha particules used
as smoke blocks these alpha particles from a source within the device, it doenst reach the detection sensor sets off the alarm
describe the radiation used in irradiating food
gamma is used to kill bacteria in food
describe the radiation used in sterilisation of medical equipment
gamma can be used
how can you determine which type of radiation is beign emmitted
by putting a paper in fron tof the source, if radistion still measured, it isnt alpha radiation, you can then put an aluminium barrier and if it is measured still it is gamma
explain radiotherapy
gamma rays used because of its low ionisation, it can kill cancer cells, patient exposed to short burtst of high intensity gamma radiation
explain medical tracing or diagnosis
low level activity gamma radiation used, injected into patients blood stream and its movement in the brain is monitored by a g-m tube outside of body
what are some adverse effects of ionising radiation
cell death, mutations and cause cancer, which might kill the organism
how are different radioactive sources safely contained
store beta and alpha in lead box
and gamma burry deep underground
what are some safety precautions when leading with ionising radiation
keep sources in lead box
do not point sources at people
keep distance from source and limit exposure
handle sourcs with long tongs
