radioactivity Flashcards
what is in the nucleus of an atom
protons and neutrons
the mass number is the
biggest number
atomic number is
the number which tells you how many protons there are
if an atom loses electrons it becomes
ionised
the number of protons determines
which element an atom is
is the atomic number always the same for an atom
yes
the mass number tells you
the number of protons and neutrons in the atom
an isotope is
an element with the same number of protons but different number of neutrons
can an element have more than 1 isotope
yes
some atomic nuclei can be unstable and
radioactive
why are some nuclei unstable and radioactive
because of an imbalance of protons or neutrons in the nucleus
how can unstable nuclei become more stable
by emiting radiation
name of the process of radioactivity to make a nuclei more stable
radioactive decay
radiation can be in the form of what (2)
high-energy particle or wave
When an unstable nucleus decays, it emits
radiation
The different types of radiation that can be emitted are:
Alpha (α) particles
Beta (β-) particles
Gamma (γ) radiation
are these changes spontaneous and random
yes
symbol for alpha
α
An alpha particle is the same as a
helium nucleus
why is an alpha particle is the same as a helium nucleus
because it consists of two neutrons and two protons
symbol for beta
β−
Beta particles are
high-energy electrons
when are beta particles produced
during beta minus decay, when a neutron in the nucleus is converted into a proton, and emits a high speed electron
symbol for gamma
γ
gamma rays are
electromagnetic waves
gamma rays have the ___ energy of the different types of electromagnetic waves
highest
Alpha (α), beta (β) and gamma (γ) radiation can be identified by their: (3)
Nature (what type of particle or radiation they are)
Ionising ability (how easily they ionise other atoms)
Penetrating power (how far can they travel before they are stopped completely)
alpha is stopped by
paper
ionising ability of alpha
high
beta particles are what
high energy electrons
beta is stopped by
aluminium foil or 10cm of air
ionising ability of beta is
moderate
gamma is what
an electromagnetic wave
gamma is stopped by
nothing
ionising ability of gamma
low
PRACTICAL- investigating penetrating power for different types of ionisation
- need a geiger-muller tube connected to a geiger counter
- without any sources present, measure background radiation over a period of one minute
- place a radioactive source a fixed distance away from the tube and take the reading of the count rate for 1 minute
- take some paper, alumunium and lead
- one at a time, place the absorbers between the source and the tube and take another reading of count rate for 1 minute
- repeat with other radioactive sources and depending on what they pass through, check if its gamma or beta or alpha
alpha particles have a mass number of _ and an atomic number of _
4
2
beta minus particles have a mass number of _ and an atomic number of _
0
-1
gamma has a mass and atomic number of
0
in alpha decay, what do you do
-4 and -2
in beta decay what do you do
add 1 to the bottom
how is ionising radiation detected
- geiger muller tube and photographic film
Photographic films detect radiation by becoming ____ when it absorbs radiation
darker
what is backround radiation
The radiation that exists around us all the time
the natural backround radiation we have comes from (2)
space and earth
sources of backround radiation (4)
radon gas (50%)
rocks and building materials (15%)
medical x-rays (13%)
food (11%)
2 types of backround radiation
Natural sources
Artificial (man-made) sources
radon gas comes from
Airborne radon gas comes from rocks in the ground, as well as building materials e.g. stone and brick
how is radon gas detected
Radon gas is tasteless, colourless and odourless so it can only be detected using a Geiger counter
cosmic rays come from
space (sun)
biological material and carbon 14
All organic matter contains a tiny amount of carbon-14
Radioactive material in food and drink
Naturally occurring radioactive elements can get into food and water since they are in contact with rocks and soil containing these elements
natural sources of backround radiation (4)
randon gas from rocks and buildings
cosmic rays from space
carbon 14 in biological material
radioactive material in food and drinks
Artificial Sources of Background Radiation (4)
nuclear medicine
nuclear waste
Nuclear fallout from nuclear weapons
Nuclear accidents
are natural backround waste usually a cause for concern
NO
nuclear waste in backround radiation
itself does not contribute much to background radiation, it can be dangerous for the people handling it
Nuclear medicine in backround radiation
In medical settings, nuclear radiation is utilised all the time
Nuclear fallout from nuclear weapons - backround radiation
Fallout is the residue radioactive material that is thrown into the air after a nuclear explosion, such as the bomb that exploded at Hiroshima
nuclear accidents backround radiation
Nuclear accidents, such as the incident at Chornobyl, contribute a large dose of radiation to the environment
While these accidents are now extremely rare, they can be catastrophic and render areas devastated for centuries
the activity of a radioactive source ____ over a period of time and is measured in ____
decreases
bequerels
The activity of a radioactive source decreases with time because
each decay event reduces the overall number of radioactive particles in the source
Activity is measured in
becquerels
Radioactive decay is a ___ process
random
half life is
the time taken for half of the radioactive nuclei in a sample to decay
half life for a given isotope is the same or different depending on size ?
same
does the line in a half life graph touch the x axis
no it gets closer but never touches it
alpha radiation is used in
smoke detectors
how do alpha particles work in a smoke detector
when there is no smoke, the alpha ionises the air forming charged particles which complete the circuit
when there is fire, smoke is produced which breaks the circuit as alpha particles are absorbed and air is no longer ionised, this causes the alarm to ring
use of beta radiation
for tracers
monitoring the thickness of materials
use of gamma radiation
destroys microorganisms on food and extends the usable lifetime of food
second use of gamma (medical)
to sterilise medical equipment
in beta radiation when monitoring the thickness of materials, what happens if its too thick
the reading becomes very low
in beta radiation when monitoring the thickness of materials, what happens if its too thin
the reading is very high
why do count rates change in a geigger muller counter ( beta)
thicker materials (lead) absorb more radiation while thinner ones absorb less
what slows gamma down
lead
what is contamination
the accidental or unwanted transfer of a radioactive substance onto or into a material
A substance is only radioactive if it contains
a source of ionising radiation
contamination happens when
a radioactive isotope gets onto a material where it should not be, and as a result the small amounts of the isotope in the contaminated areas will emit radiation and the material becomes radioactive
what is irridation
The process of exposing a material to ionising radiation
does irradiating a substance make it radioactive
NO
what can irradiating a substance cause
cells to be killed
contamination is usually an
accident
irradiation is usually
on purpose
example of irradiation
sterilisation of food or medical equipment
when is medical equipment irradiated
before being used in order to kill any micro-organisms on it before surgery
when is food irradiated
d to kill any micro-organisms within it to make it last longer
radiation can cause harm in two ways, what are they
irradiation and contamination
how is ionising radiation harmful to living things
- kills and ionises living cells ( tissue cells)
- mutations of cells
tissue damage through radiation usually happens by
high energy EM radiation (like gamma rays)
what happens in mutation of cells by radiation (3)
- atoms in the DNA are ionised
- DNA can mutate while repairing
- if they replicate then it means that they form a tumour
precautions that can be taken to reduce radiation waste (3)
- increase distance from source (which reduces intensity and chance of contamination)
- reduce time spent near the source (decreases amount of radiation recieved)
- shielding (reduces amount of radiation which reaches the user)
by-products of nuclear power production often have __ half lives
Meaning …
LONG
they could remain a risk for thousands of years
what precaution is taken to get rid of by products of nuclear power production and why
storing them underground as it reduces the risk because not even gamma can pass through large amounts of earth and rock
