Radioactivity Flashcards
Protons and neutrons are packed tightly in the ______, where
you find most of the atom’s mass.
nucleus
- allows protons and neutrons to be attracted to each other.
- 4x stronger than electric force
- short-range
Strong Nuclear Force
- Chemicals with isotopes in which the arrangement of protons and neutrons is less than ideal.
- these elements exhibit a degree of nuclear instability
Radioactive
Isotopes which spontaneously emit radiation
Radio-isotopes
the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves
Radioactive decay
Radioactivity is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of ___ or ____
particles or electromagnetic waves
An unstable _____ releases energy to become more stable
nucleus
After decaying, ____________“change” into other atoms
radioactive atoms
Father of Radioactivity
Henri Becquerel (1896)
In <year>, <name> discovered, almost by accident, that uranium
can blacken a photographic plate, even in the dark.</name></year>
Henri Becquerel (1896)
In 1903, he shared the Nobel Prize in Physics with ____ and
________ “in recognition of the extraordinary services he
has rendered by his discovery of spontaneous radioactivity”.
Pierre and Marie Curie
Nobel Prize in Chemistry
Marie Curie (1911)
They discovered other natural
radioactive elements such as
: Radium and Polonium.
Marie and Pierre Curie
Marie and Pierre Curie discovered other natural radioactive elements such as
Radium and Polonium
Radioactive material such as______ first discovered by Henri Becquerel
Uranium
According to M. Curie, the activity of
* 1g Ra = 1Ci = 3.7 x10^10 decays/s or
DPS
1Bq = ____
1 decay/s or DPS
5 sources of radioactivity:
- Primordial
- Cosmogenic
- Human Produced
- Naturally Occurring Sources
- Manmade Sources
sources of radio activity
from before the creation of the Earth
Primordial
Sources of radioactivity
formed as a result of cosmic ray interactions
Cosmogenic
sources of radioactivity
enhanced or formed due to human
actions (minor amounts compared to natural)
Human produced
sources of radioactivity
- Radon from the decay of Uranium and Thorium
- Potassium -40 – found in minerals and in plants
- Carbon 14 – Found in Plants and Animal tissue
Naturally Occuring Sources
sources of radioactivity
- Medical use of Radioactive Isotopes
- Certain Consumer products –(e.g. Smoke detectors)
- Fallout from nuclear testing
- Emissions from Nuclear Power plants
Manmade sources
2 Types of radio activity
- natural
- artificial
Types of radioactivity
By existence, there are elements here on Earth that
is radioactive (ex. uranium, thorium, radium)
Natural Radioactivity
The first major advance
occurred in 1930’s with
the invention of the
cyclotron by **Ernest
Lawrence **in Berkeley,
California.
Artificial Radioactivity
- Enrico Fermi in Rome started
systematically exposing the elements
in the Periodic Table to beams of
neutrons. - Identified 40 new radio-active species and thus was able to show how neutrons that
had been slowed down prior to
interacting with the targets gave
rise to much higher levels of
radioactivity
Artificial radioactivity
- identified around 40 new
radio-active species and thus was
able to show how neutrons that
had been slowed down prior to
interacting with the targets gave
rise to much higher levels of
radioactivity.
*_____in Rome started
systematically exposing the elements
in the Periodic Table to beams of
neutrons.
Enrico Fermi
is the energy that is released as particles or
rays, during radioactive decay.
Radiation
- is the property of an atom that describes
spontaneous changes in its nucleus that create a different element. - These changes usually happen as emissions of **alpha or beta particles and often gamma rays. **
Radioactivity
The rate of emission is referred to as a material’s _____
activity
Each occurrence of a nucleus throwing off particles or energy is referred to as a ______
disintegration
The number of disintegrations per unit time (minutes, seconds, or hours) is called the ____
activity of a sample
activity is expressed in ___
curies
1 curie =
37 billion dps
DPS
disintegrations per second
Units of Activity
*Curie (Ci)
*Becquerel (Bq)
*disintegration per second (dps)
applications for radioactivity
produced during World War II
in Berlin
On the back of the tube it was
stated that, ‘radioactive
radiation increases the defense
of teeth and gums… cells are
loaded with new life energy, the
destroying effect of bacteria is
hindered… it gently polishes the
dental enamel and turns it white
and shiny.’
Doramad radioactive toothpaste
In the U.S, hundreds of thousands of people
began drinking bottled water laced with
radium, as a general elixir known popularly
as ____
liquid sunshine
1952 LIFE magazine wrote
about the beneficial effects of inhaling
__________in deep mines.
radioactive radon gas
1953, a company in Denver was
promoting a radium-based _________
contraceptive
jelly
Atoms found in nature are either ____ or____
stable or unstable
An atom is _____ if the forces among the
particles that makeup the nucleus are balanced.
stable
An atom is ______ (radioactive) if these forces
are unbalanced–if the nucleus has an excess of
internal energy
unstable
An atom is unstable (radioactive) if these forces
are unbalanced–if the nucleus has an excess of
______
internal energy
causes atoms to be radioactive
Instability of an atom’s nucleus
may result from an excess of
either neutrons or protons.
How long do radionuclides stay radioactive?
*It depends on the kind of radioactive material.
*The rate of decay (half-life) is one of the characteristics of
radionuclides.
- is the time required for the disintegration of
one-half of the radioactive atoms that are present when
measurement starts. - It does not represent a fixed number of atoms that
disintegrate, but a fraction
*Half-life (t1/2)
3 types of half life
- physical
- biological
- effective
the time it takes for a radioactive atom to half
its original activity by 50%.
physical half-life
- is the time an organism takes
to eliminate one half the amount of a compound or chemical on a strictly biological basis. - Thus, if a stable chemical compound were given to an individual and half of it were eliminated by the body (perhaps in urine) within three hours, the ________ half-life would be three hours.
biological half-life
- incorporates both the radioactive
and biological half-lives. - It is used when health physicists calculate the dose
received from an internal radiation source.
Effective Half-life
To determine the effective half-life of a radionuclide in a
human, one needs to know the _______ half-life as
well as the ____ half-life of the radionuclide.
radioactive; biological
_____tells how quickly the
radioactivity from the radionuclide will
decrease.
_____tells how active it
is now
half-life; number of curies
As the nucleus emits radiation or disintegrates, the radioactive atom or radionuclide transforms to different ________. The process is called radioactive decay.
nuclides
Can unstable atoms become stable?
continue radioactive decay until the forces in the nucleus are balanced
(STABLE)
A radioactive atom will attempt to reach stability by
throwing off ____
nucleons
This decay chain, or decay series, ends in a _________
stable nuclide
*Until the last step, these radionuclides emit energy or
particle with each transformation and become another
radionuclide.
Decay Chains
Radionuclide decay chains are important in
planning for the _______________ of
radioactive materials and waste and for ___________
management and disposal;site cleanup.
As radioactive decay progresses, the concentration of the original radionuclides decreases, while the concentration of their decay products increases and then ________ as
they undergo transformation.
decreases
As radioactive decay progresses, the concentration of the
original radionuclides _______, while the concentration
of their decay products increases and then decreases as
they undergo transformation.
decreases
The increasing concentration of
decay products and activity is called
ingrowth
for a decay chain occurs when
each radionuclide decays at the same rate it is produced.
Radioactive equilibrium
When the production and decay rates of each radionuclide
in the decay chain are equal, the chain has reached
radioactive equilibrium.
However if the half-life of the decay product is much
longer than that of the original radionuclide,
equilibrium
cannot occur.
Types of Radioactive
Equilibrium
The original radionuclide
and decay product half-lives
are similar
transient
equilibrium
Types of Radioactive
Equilibrium
The original radionuclide
has a much longer half-life
secular equilibrium
Types of Radioactive
Equilibrium
The decay product has a longer
half-life
no equilibrium
Modes of Radioactive Decay
Stable nuclides of the lighter
elements have approximately equal
numbers of protons and neutrons.
However, as Z(number of protons) increases, the `**stability
line’ curves upwards.
Heavier nuclei need more and more
neutrons to be stable.
Stability
Modes of Radioactive Decay
A radio-nuclide above the
stability line decays by
β-emission.
Because it loses a neutron
and gains a proton, it
moves diagonally towards
the stability line, as shown
on this graph.
Beta decay
A plot of neutron number versus proton
number is also called .
Segre plot
Modes
of Radioactive
Decay
A radio-nuclide above the
stability line decays by
β-emission.
Beta decay
stable or unstable?
1:1 for _____ elements, and 3:2 for ____.
smaller; bigger
- is a sub-atomic particle with a small mass (similar to
electrons) and no electrical charge. - not affected by the electrical or magnetic
forces. It is shown by the letter ѵ(nu).
neutrino
The neutrino was postulated first
by ________ in 1930 to
explain how beta decay could
conserve energy
Wolfgang Pauli
____________ discovered a
much more massive nuclear
particle in 1932 and also named it a
neutron
James Chadwick
coined the
term neutrino (the Italian
equivalent of “little neutral one”)
Enrico Fermi
is an antimatter particle,
the counterpart to the neutrino.
antineuterino
Occurs when the nucleus is too
large
Alpha Particle Emission/decay
When the ratio of neutrons to
protons in the nucleus is too low,
certain atoms restore the balance
by emitting ___________.
alpha particles
________ emitting atoms tend to be
very large atoms (high atomic
numbers).
alpha
With some exceptions, naturally
occurring alpha emitters have
atomic numbers of at least __ (the
element lead).
82 (lead)
What happens to atoms during alpha emission?
alpha particle is ejected
leaving The atom has then lost
two protons along with two
neutrons.
Net effect is loss of 4 in mass
number and loss of 2 in
atomic number.
alpha emission
occurs when the
neutron to proton ratio is too
great in the nucleus and
causes instability.
- Many radioactive nuclides
decay by β-emission
beta decay
Beta decay
What happens is that one of
the _____ changes into a
proton (which stays in the
nucleus) and an electron
(which is emitted as a
β-particle).
neutrons
particle with
same mass as an electron
but with a positive charge
(antimatter version of an
electron)
positron
The atomic number goes UP by one and mass number remains
unchanged.
Beta Minus Decay
The atomic number goes DOWN by one and mass number remains
unchanged.
Positron Decay
A nuclear process in which a
nucleus with excess energy
following the emission of an
alpha particle or a beta
particle *emits energy without
changing its number
of protons or neutrons. *
Isomeric Transition
occurs because the nucleus
is at too high an energy.
gamma decay
Sometimes a nucleus that is still unstable
after a beta or alpha decay is still unstable
so may emit ________ to become
more stable.
gamma radiation
is a process in
which a nucleus with excess energy
can get rid of that energy *without
altering its proton or neutron
count. *
Internal Conversion
- It can occur only if the amount of
energy given to the orbital electron
exceeds its binding energy. - X-rays are emitted as the atom
attempts to restore its neutrality
Internal Conversion
Thorium 232
Lead 208
—- from the decay of uranium and thorium
Radon
found in minerals and plants
Potassium-40
found in plants and animal tissue
Carbon 14
Uranium 238
Lead 206
Uranium 235
Lead 207
Neptunium 237
Bismuth 209
Neptunium 237
Bismuth 209
