Nuclear Chemistry Flashcards
In his experiments, he exposed certain salts—among them uranium salts—to sunlight for several hours, whereupon they phosphoresced.
Henri Becquerel
Three kinds of radiation
alpha, beta, gamma
helium nuclei
Alpha particles
are electrons. Each has a charge of 21.
Beta particles
are high-energy electromagnetic radiation.
Gamma rays
the distance from one wave crest to the next.
wavelength
the number of crests that pass a given point in one second.
frequency
Electromagnetic radiation comes in packets; the smallest units are called
photons
are electromagnetic radiation of very high frequency (and high energy).
Gamma rays
are electromagnetic radiation of very high frequency (and high energy).
Gamma rays
has frequencies (and energies) higher than those of visible light but less than those of gamma rays.
X-rays
Materials that emit radiation (alpha, beta, or gamma) are called
radioactive
A radiation emitting isotope of an element
Radioactive isotopes
A reaction that changes atomic nuclei of elements
(usually to atomic nuclei of other elements)
Nuclear reaction
The proton remains in the nucleus but the electron is emitted from it.
Beta emission
The changing of one element into another is called
transmutation
emits both an a particle and gamma rays
Polonium-210
Is a particle that has the same mass as an electron, but a charge of 11 rather than 21.
Positron
often accompanies a and b emissions
Gamma emission
an extranuclear electron is captured by the nucleus and there reacts with a proton to form a neutron.
Electron capture
The time it takes for one half of any sample of radioactive material to decay is called the
Half-life
most of the radioactivity disappears
after _______ by that time, only _____ of the original remains
5 half-lives, 3%
After ______ half-lives, less than _______ of the activity remains.
10, 0.1%
The half-life of an isotope is independent of
temperature and pressure
When these rays interact with matter, they usually knock electrons out of the electron cloud surrounding an atomic nucleus, thereby creating
positively charged ions from neutral atoms.
Ionizing radiation
Ionizing radiation is characterized by two physical measurements
Intensity and energy
which is the number of particles or photons emerging per unit time
Intensity
Instruments used to measure intensity
Geiger-Muller counter and proportional counter
material called a phosphor that emits a unit of light for each alpha or beta particle or gamma ray that strikes it.
Scintillation counters
A commonly used unit of radiation intensity is the
Curie
much smaller, unit of radiation activity (intensity) is the
Becquerel
beta particles have an energy range of
1 to 3 MeV
the least penetrating; they can be stopped by several sheets of ordinary paper, by ordinary clothing, and by the skin
Alpha particles
have greater penetrating power; They can penetrate several millimeters of bone or tissue.
Beta particles
is the most penetrating of the three types of radiation. They can pass completely through the body
Gamma radiation
when in the body, are more damaging, however
Alpha particles
are a measure of the energy delivered by a radiation source and are, therefore, a measure of exposure to a particular form of radiation.
Roentgens
which stands for radiation absorbed dose, is a measure of the radiation absorbed from a radiation source.
Rad
SI unit of rad
Gray = 100 rad
which stands for roentgen equivalent for man, is a measure of the effect of the radiation when a person absorbs 1 roentgen.
Rem
SI unit for rem
sievert = 100 rem
Naturally occurring radiation
background radiation
is the most widely used aspect of nuclear medicine.
Medical imaging
This method is based on the property that certain isotopes (such as carbon-11 and fluorine-18) emit positrons
Positron emission tomography
is used in the treatment of prostate
cancer.
Iodine-25
The fusion of two hydrogen nuclei into a helium nucleus liberates a very large amount of energy in the form of photons
Fusion
Uncontrolled fusion is employed in the
Hydrogen bomb
are artificial and have been prepared by a fusion process in which heavy nuclei are bombarded with light ones.
Transuranium elements
Transuranium elements
elements with atomic numbers greater than 92
fragmentation of large nuclei into smaller pieces
Nuclear fission
The most important product of this nuclear decay is energy, which results because the products have less mass than the starting materials.
Atomic energy
If even one of these neutrons produces a new fission, the process becomes a self-propagating _______ that continues at a constant
rate.
Chain reaction
is the combining (fusing) of two
lighter nuclei to form a heavier nucleus.
Nuclear fusion
results from the bombardment of nuclei by neutrons, protons, or other nuclei.
nuclear transmutation
like charges repel and unlike charges attract one another.
Coulomb’s law
The principal factor that determines whether a nucleus is stable is the
neutron to proton ratio
The numbers 2, 8, 20, 50, 82, and 126
are called
magic numbers
Rules in predicting nuclear stability
- Magic numbers for proton and neutrons
- Even numbers of proton and neutron are more stable than odd numbers
- All isotopes with atomic number higher than 83 are radioactive
The stable nuclei are located in an area of the graph known as the
belt of stability
the energy required to break up a nucleus into its component protons and neutrons.
Nuclear binding energy
which is a general term for the protons and neutrons in a nucleus.
nucleons
The difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons is called
mass defect
a sequence of nuclear reactions that ultimately result in the formation of a stable isotope
radioactive decay series
uses electric and magnetic fields to increase the kinetic energy of charged species so that a reaction will occur
Particle accelerator
The first nuclear fission reaction to be studied was that of
Uranium-235
the minimum mass of fissionable
material required to generate a self-sustaining nuclear chain reaction
critical mass
Most of the nuclear reactors in the United States are
light water reactors
substances that can reduce the kinetic energy of neutrons.
moderators
it eliminates the need for building expensive uranium enrichment facilities.
Heavy water reactors
uses uranium fuel, but unlike a conventional nuclear reactor, it produces more fissionable materials than it uses
Breeder reactor
are dangerous radioactive isotopes with long half-lives
Strontium-90
used as a nuclear fuel and produced in breeder reactors, is one of the most toxic substances known.
Plutonium-239
fusion reactions take place only at very high temperatures, they are often
called
thermonuclear reactions
state of matter, a gaseous mixture of positive ions and electrons
plasma
Isotopes, especially radioactive isotopes that
are used to trace the path of the atoms of an element in a chemical or biological
process
tracers
molecular fragments having one or more unpaired electrons; they are usually short lived and highly reactive.
radicals
