7 Radioactivity and Particles Flashcards
Describe the structure of an atom in terms of protons, neutrons and electrons
tiny, dense nucleus (made up of protons and neutrons) at their centre, with electrons orbiting around the nucleus in shells
Define atomic(proton) number
number of protons in an atom - always the same
Define mass(nucleon) number
number of protons and neutrons in nucleus
Define isotope
Atoms with the same number of protons but different numbers of neutrons
How are alpha (α) particles, beta (β−) particles, and gamma (γ) rays emitted ?
ionising radiations emitted from unstable nuclei in a random process
RADIOACTIVITY AND PARTICLES
units for:
frequency of decay :
distance :
time :
frequency of decay : becquerel (Bq), 1 (Bq) for 1 decay / sec
distance : centimetres (cm), normally however is (m)
time : hour (h), minute (min) but normally (s)
describe structure of an atom
Atoms are made up of protons, neutrons and electrons.
Protons and neutrons are in the nucleus, electrons are in the shells
define:
atomic number
mass number
isotope
Atomic (proton) number is the number of protons in the nucleus of an atom.
Mass (nucleon) number is the total number of protons and neutrons in the nucleus of an atom.
An isotope is an atom of the same element, same number of protons, different number of neutrons
alpha (α) particles, beta (β−) particles, and gamma (γ) rays are ionising radiations emitted from ______ nuclei in a ______ process
unstable
random
can one radioactive source release different types of radiation?
yes
what is ionisation
when an atom loses or gains an electron, causing it to become an ion (an atom which is positively or negatively charged).
describe nature of alpha (α) particles
ionising
penetration
stopped by:
nature of radiation:
strong ionising
weak penetration
stopped by paper
nature of radiation: helium nucleus
4
He
2
describe nature of alpha (α) particles
ionising
penetration
stopped by:
nature of radiation:
moderate ionising
moderate penetration
stopped by: 5mm aluminium
nature of radiation: fast moving electron
0
e
-1
describe nature of gamma (γ) rays
ionising
penetration
stopped by:
nature of radiation:
weak ionising
strong penetration
stopped by: 10cm lead
nature of radiation: em wave
0
γ
0
practical: investigate the penetration powers of different types of radiation using either radioactive sources or simulations
Detect using a Geiger Müller Tube.
Try the three different materials in order, paper then aluminium then lead.
Count rate will significantly decrease if radiation is stopped.
describe alpha decay in terms of atomic and mass numbers
2 protons and 2 neutrons are lost.
· Mass number decreases by 4
· Atomic number decreases by 2
describe beta decay in terms of atomic and mass numbers
· 1 neutron is converted to an electron (lost from the atom) and proton
· Mass number is unchanged
· Atomic number increases by 1
describe gamma decay in terms of atomic and mass numbers
· Energy is lost from an atom in the form of an electromagnetic wave
· Mass number is unchanged
· Atomic number is unchanged
describe neutron radiation in terms of atomic and mass numbers
In neutron-rich nuclides, occasionally one or more neutrons are ejected. They are also emitted during nuclear fission.
The nucleus becomes a new isotope of the original element
Photographic film:
Radiation will cause photographic film to ______ . They are worn as badges by people who work with radiation, to check how much exposure they have had
darken
sources of background (ionising) radiation from Earth and space
radon in air
Granite in rocks
Cosmic rays
Medical equipment - x rays from mri scanners
Food and drink containing radioactive isotopes
Geiger Müller detector:
When connected to a counter, the detector will be able to measure _________ . Each time it absorbs radiation, it transmits an electrical pulse to the machine, which
produces a clicking sound. The greater the frequency of clicks, the more radiation present.
radioactivity
activity of a radioactive source ______ over a period of time and is measured in ___________
decreases
becquerels
define half life
time taken for the radioactivity of a specific isotope to fall to half its original value.
uses of radioactivity in industry
smoke detectors
thickness monitoring for metal sheets
o Smoke detectors
Long half-life alpha emitters are used in smoke detectors. Alpha particles cause a current in the
alarm. If smoke enters the detector, some of the alpha particles are absorbed and the current drops, triggering the alarm.
o Thickness monitoring
Long half-life beta emitters can be used for thickness monitoring of metal sheets. A source and receiver are placed on either side of the sheet during its production. If there is a drop or rise in the number of beta particles detected, then the thickness of the sheet has changed and needs to be adjusted.
contamination
what is it?
what does it do?
source?
prevention?
causes?
Contamination:
Occurs when material that contains radioactive atoms is deposited on materials, skin, clothing, or any place where it is not desired.
- object exposed to radiation t become radioactive
- Irradiating a material does not make that material radioactive. However, it can kill living cells
3.source is from radiation emitted outside of the object
4.prevent by using shielding, such as lead clothing
5.caused by the presence of radioactive sources outside the body
Alpha
describe the dangers of ionising radiations, including: that radiation can cause mutations in living organisms, that radiation can damage cells and tissue, the problems arising from the disposal of radioactive waste and how the associated risks can be reduced.
Beta
describe the dangers of ionising radiations, including: that radiation can cause mutations in living organisms, that radiation can damage cells and tissue, the problems arising from the disposal of radioactive waste and how the associated risks can be reduced.
low-activity sources used in smoke alarms
Gamma
describe the dangers of ionising radiations, including: that radiation can cause mutations in living organisms, that radiation can damage cells and tissue, the problems arising from the disposal of radioactive waste and how the associated risks can be reduced.
define nuclear fission
splitting of a large and unstable nucleus into two smaller and more
stable nuclei to produce energy. This is the method currently used in nuclear power stations
define nuclear fusion
process where lighter atoms are forced to join together to make heavier atoms. This releases energy.
what is radioactive decay
random process involving unstable nuclei emitting radiation to become more stable.
nuclear fusion, nuclear fission and radioactive decay all can be sources of ________
energy
explain the alpha decay process
- heavy (helium) nucleus emits an alpha particle
- nucleus changes to that of a different element
explain the beta decay process
A neutron turns into a proton and emits a beta particle (electron)
The nucleus changes to that of a different element
explain gamma decay process
After a previous decay, a nucleus with excess energy emits a gamma particle.
Gamma particles are a form of electromagnetic radiation.
uses of radioactivity in medicine
o Sterilisation of equipment
Gamma emitters are used to kill bacteria or parasites on equipment so it is safe for operations (this means they can be sterilised through their protective packaging to eliminate the risk of contamination).
o Diagnosis and treatment
- Short half-life gamma emitters such as technetium-99m are used as tracers in medicine as they concentrate in certain parts of the body. The half-life must be long enough for diagnostic procedures to be performed, but short enough to not remain radioactive for too long.
- Other gamma emitters such as cobalt-60 can be used to destroy tumours with a high dose
of radiation.
irradiation
what is it?
what does it do?
source?
prevention?
causes?
- object exposed to radiation but does not become radioactive
- Irradiating a material does not make that material radioactive. However, it can kill living cells
3.source is from radiation emitted outside of the object
4.prevent by using shielding, such as lead clothing
5.caused by the presence of radioactive sources outside the body
what are the products of nuclear fission and what is released
the process of splitting a nucleusa uranium-235 nucleus absorbs a thermal (slow-moving) neutron, it splits into two
daughter nuclei and 2 or 3 neutrons, releasing energy in the process.
what can the products of nuclear fission do
neutrons then can induce further fission events in a chain reaction by striking other
uranium-235 nuclei
describe uses in a nuclear reactor :
control rods
moderator
reactor
- boron - absorbs neutrons and keeps number of neutrons that only one fission neutron per event goes on to induce further fission
- water - slows down neutrons by collisions so they move slow enough to be absorbed by another u-235 nucleus
- thick steel vessel - withstands high pressure and temperatures and absorbs some radiation. has concrete walls that act as radiation shields to absorb all radiation escaping reactor core
define chain reaction
neutrons then can induce further fission events in a chain reaction by striking other uranium-235 nuclei
how to dispose of radioactive waste
geographically stable, sealed in glass blocks in lead lined boxes, buried deep underground
away from people as could leach into groundwater amd contaminate soil, rivers and drinking water
explain process of nuclear fusion
the process of fusing two nuclei to form a larger nucleus, results in a loss of mass from smaller nuclei and release of energy
explain process of nuclear reactor
substance pumped around reactor
energy from fission transfers the energy to water by heating
water into steam
steam turns turbine
turbine turns generator
generator produces electricity
how do sun and stars release energy
nuclear fusion
why does nuclear fusion not occur at low temperatures
● Nuclear fusion does not happen at low temperatures and pressures because the
electrostatic repulsion of the protons is too great.
