C.W. BAKER HIGH SCHOOL
Nuclear Chemistry Outline
Prepared by M.
Types of Nuclear Reactions
Radioactive Decay the nuclei of some atoms are unstable, and
may spontaneously emit small particles
leaving behind an atom of a new element.
Atoms that undergo radioactive decay are called radioisotopes.
Types of natural radioactive decay
Alpha decay some unstable atoms will
emit an alpha particle. An alpha
particle is a nucleus of a helium atom composed of two protons and two
neutrons. It can be represented by the
Greek letter a or by 42He. Alpha particles carry a charge of +2.
Beta decay some unstable atoms will
emit a beta particle. A beta particle
is essentially an electron (which is emitted from the nucleus). It can be represented by the Greek letter B or by 10e. Beta particles carry a charge of -1.
Gamma radiation in addition to alpha
and beta particles, unstable nuclei may emit high energy photons of
electromagnetic radiation during radioactive decay. These photons are call gamma rays and can be represented by g.
Gamma rays have no charge and no detectable mass.
decay mode for various radioisotopes can be identified by looking in Chart N
of the Reference Tables.
different types of radioactive decay particles can be identified by passing
them through an electric field as shown below:
The Beta particles are attracted
to the positive plate due to their negative charge, while the alpha particles
are attracted toward the negative plate due to their positive charge. Gamma rays are not attracted toward either
plate because they have no charge.
Notice that the beta particles are deflected more than the alpha
particles. This is because the alpha
particles have more mass and are harder to deflect than the much lighter beta
rate at which a sample of atoms undergoes radioactive decay cannot be
The time which it takes for one half of a sample of an
atom to undergo radioactive decay is called the half-life.
Fusion a process by which smaller atoms are combined
together to form larger atoms. This
process is responsible for the energy given off by stars (including the Sun).
In stars, such as our Sun, hydrogen atoms
combine together to produce helium atoms.
bombs (thermonuclear devices) are utilize the fusion process.
and engineers are trying to make controlled fusion reactors. Hopefully, these attempts will eventually
result in a new and abundant source
Fission a process by which large atoms split into two
smaller atoms, producing energy and neutrons.
Two isotopes are utilized in fission reactions
U 235 (Uranium 235)
neutrons that are produced in one fission reaction can strike other U-235 atoms
and cause them to undergo fission. This
process is called a nuclear chain reaction.
The minimum amount of fissionable material required to
sustain a chain reaction is called the critical mass.
Mass-energy conversions in nuclear reactions
Unlike chemical reactions,
the total mass of the reactants is not equal to the total mass of the reactants
in a nuclear reaction. The difference
in mass is called the mass defect.
The mass which appears to be
lost in the reaction is actually converted into energy. The equation E = Dm
x c2 can be used to find out how
much energy is produced for a given quantity of mass.
The quantity of energy produced in chemical reactions is much
greater than in chemical reactions.
fusion reactions involve the greatest mass defect, they produce the most energy
Writing Balanced Nuclear Reactions
Law of Conservation of Mass Number the total of the mass numbers
of the reactants must equal the total of the mass numbers of the products.
Law of Conservation of Atomic Number the total of the atomic
numbers of the reactants must equal the total of the atomic numbers of the
utilizing the two laws it is possible to predict the products of nuclear
reactions: For example: Predict the product of the beta decay of
we write the reactant atom (C-14) and show it giving off a beta particle (-10e)
Then, utilizing the laws of conservation of mass number
and atomic number, determine the mass number and atomic number of the other
Finally, determine the symbol of the atom by looking it
up in the Periodic Table.
Applications involving nuclear reactions
Nuclear power plants utilize the fission reaction to generate
heat. The heat is used to drive
turbines/generators and create electricity.
fissionable material is held within the reactor cores as pellets packed inside
of metal tubes called fuel rods.
rate that neutrons released from one fission are allowed to cause subsequent
fissions is controlled by the control rods. These control rods are made of boron or
cadmium steel and absorb neutrons preventing them from striking other
fissionable atoms and causing additional fissions.
chance of neutrons causing atoms to undergo fission is increased by slowing the
neutrons down. Modern reactors utilize
water or graphite to slow down the neutrons and increase the likelihood of fissions taking
place. These substances are called moderators.
¨ Water often time serves a dual
purpose in a reactor, functioning both as a coolant and a moderator.
Advantages of nuclear power
¨ Relatively small amount of
fuel provides a large amount of energy.
¨ While operating, release no
pollution into the atmosphere. Fossil
fuel plants release greenhouse gases and cause acid rain.
Disadvantages of nuclear power
of fission are radioactive with long half-lives. Disposal requires isolating waste products for thousands of
to the environment if radioactive material in core is released due to some form
of accident within the plant.
Dating samples using radioactive half-lives - by analyzing the amount of undecayed radioactive
isotopes it is possible to determine the length of time that a sample has been
undergoing radioactive decay, and thus the age of the sample.
Carbon-14 Dating compares the amount of
radioactive C-14 left in a sample with the amount of the isotope which was
originally present in the sample. Used
primarily for dating organic material (things which were once alive).
U-238 Pb-206 series - U-238 undergoes a number of steps in
eventually decaying into the stable isotope of Pb-206. By comparing the relative amounts of the
U-238 and the isotopes produced in the decay it is possible to determine the
age of a sample. Used primarily in
determining the age of rocks.
K-40 Ar-40 another substance with a very
long half-life that makes it ideal for determining the age of very old rocks.
Iodine-131 used in the treatment of thyroid disease.
Cobalt-60 used to irradiate cancers. Cancerous growths, due to their rapid rate
of cell division, are more vulnerable to radiation than normal cells.