GE-CHEM 1103 Module 4.2 Flashcards
composed of the
two nucleons, protons and neutrons
nucleus
number of protons
atomic number (Z)
number of protons and neutrons together
mass number (A)
Not all atoms of the same element have the
same mass, due to different numbers of
neutrons in those atoms
Isotopes
nuclei change spontaneously,
emitting radiation
radioactive and refer to these nuclei’s as radionuclides
show how
these nuclear reactions occur
nuclear equations
atoms and
charges need to balance
chemical equations
atomic number
and mass number need to balance
nuclear equations
Has a charge of 2+, a mass of 6.64x10^-24 g, a relative penetrating power of 1 and its nature of radiation is 4(A) 2(Z) He nuclei
α
Has a charge of 1-, a mass of 9.11x10^-28 g, a relative penetrating power of 100 and its nature of radiation is electrons
β
Has a charge of 0 , a mass of 0 g, a relative penetrating power of 10000 and its nature of radiation is high-energy photons
γ
How far do the alpha, beta, neutron and gamma radiation pass through materials
paper(alpha) > hand (skin) > metal(beta) > water (neutron)> concrete > lead(gamma)
Nuclear Equation:
(A)(Z) X > (A-4)(Z-2) Y + 4(A) 2(Z) He
Change in atomic no.: -2
Change in mass no.: -4
Alpha decay
Nuclear Equation:
(A)(Z) X > (A)(Z+1) Y + 0(A) -1(Z) e
Change in atomic no.: +1
Change in mass no.: no change
Beta decay
Nuclear Equation:
(A)(Z) X > (A)(Z-1) Y + 0(A) +1(Z) e
Change in atomic no.: -1
Change in mass no.: no change
Positron emission
Nuclear Equation:
(A)(Z) X + 0(A) -1(Z) e > (A)(Z-1) Y
Change in atomic no.: -1
Change in mass no.: no change
Electron capture
loss of an α-particle
(He-4 nucleus, two protons and two neutrons):
Alpha decay
is the loss of a β-particle (a
high-speed electron emitted by the nucleus)
Beta decay
is the loss of a γ-ray,
which is high-energy radiation that
almost always accompanies the loss of
a nuclear particle
Gamma emission
a particle that has the same
mass as, but an opposite charge to, that
of an electron
positron
Some nuclei decay by emitting a
positron
Positron Emission
An electron from the surrounding electron
cloud is absorbed into the nucleus
electron capture
Writing Nuclear Equations for
Nuclear Transmutations
Example
(A)(Z) X(α, p) (A)(Z) Y
first-order process
Radioactive decay
The kinetics of such a process obey this
equation
ln(Nt/No) = -kt
time required for half of a radionuclide
sample to decay.
Half-life
Formula of k constant
k = ln 2 (or 0.693)/t 1/2
radioisotopes used to
study a chemical reaction
Radiotracers
An element can be followed through a
reaction
to determine its path and better
understand the mechanism of a chemical
reaction
react chemically exactly the
same as nonradioactive nuclei of the same
element
Radionuclides
Medical Application of Radiotracers
- wide diagnostic use in medicine
- administered to a patient (usually
intravenously) and followed. Certain elements collect more in certain tissues, so an organ or tissue type can be studied based on where the radioactivity collects.
- A compound labeled
with a positron emitter
is injected into a
patient. - Blood flow, oxygen and
glucose metabolism,
and other biological
functions can be
studied. - Labeled glucose is
used to study the brain,
as seen in the figure to
the right.
Positron Emission Tomography
(PET Scan)
There is a tremendous amount of
energy stored in nuclei.
* Einstein’s famous equation, E = mc2
relates directly to the calculation of
this energy.
Energy in Nuclear Reactions
associated with making and
breaking chemical bonds
Chemical energy
due to changes in the nucleus of
atoms changing them into different atoms
Nuclear energy
13% of worldwide energy
nuclear energy
Commercial nuclear power plants
fission
Bombardment of the radioactive nuclide with a neutron starts the process
Nuclear Fission
Neutrons released in the transmutation strike other nuclei,
causing their decay and the production of more neutrons.
(note: This process continues on and on)
chain reaction
rate of neutron loss > rate of neutron creation by fission
Subcritical mass
rate of neutron loss = rate of neutron creation by fission
Critical mass
rate of neutron loss < rate of neutron creation by fission
Supercritical mass
The minimum mass that must be present for a chain reaction to be sustained
critical mass
the heat generated by the reaction is
used to produce steam that turns a turbine connected to a
generator.
nuclear reactors
What does The reactor core
consists?
fuel rods,
control rods,
moderators, and
coolant
block the paths of some
neutrons, keeping the
system from reaching
a dangerous supercritical mass
control rods
- Reactors must be stopped periodically to
replace or reprocess the nuclear fuel. - They are stored in pools at the reactor site.
- The original intent was that this waste
would then be transported to reprocessing
or storage sites. - Political opposition to storage site location
and safety challenges for reprocessing
have led this to be a major social
problem.
Nuclear Waste
When small atoms are combined, much energy is
released. This occurs on the Sun. The reactions are
often called thermonuclear reactions.
Nuclear Fusion
more harmful to living systems
Ionizing radiation
any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules that is, to completely remove an electron from an atom or molecule.
nonionizing radiation
depends on the type
of radioactivity, the
length of exposure,
and whether the
source is inside or
outside the body.
damage to cells
Outside the body it is the most dangerous
gamma rays
Inside the body it can cause most harm
alpha
radiation
- Low-level, long-term exposure can cause health issues.
- Damage to the growth-regulation mechanism of cells
results in cancer.
Exposure in radiation
