Transcript File
Chapter 10
Nuclear Chemistry
Objectives:
1. Describe the process of nuclear
decay
2. Classify nuclear radiation as alpha
particles, beta particles or gamma
rays
3. Balance nuclear equations
4. Identify sources of nuclear
radiation and describe how nuclear
radiation affects matter
5. Describe methods of detecting
nuclear radiation
Definition:
radioactivity is the
process in which an unstable
atomic nucleus emits charged
particles and energy
Definition: a radioisotope is any
atom containing un unstable
nucleus
During nuclear decay, atoms of
one element can change into
atoms of a different element
altogether
Definition: an alpha particle is a
positively charged particle made up
of two protons and two neutrons (the
same as a helium nucleus)
In alpha decay the product isotope
has two fewer protons & two fewer
neutrons than the reactant isotope
Definition: a beta particle is an
electron emitted by an unstable
nucleus
In beta decay the product isotope has
one proton more and one neutron
fewer than the reactant isotope
Definition: a gamma ray is a
penetrating ray of energy emitted by
an unstable nucleus
Gamma radiation has no mass and
no charge
During gamma decay the atomic
number & mass number remain the
same, but the energy of the nucleus
decreases
Gamma radiation is very penetrating
compared to the alpha and beta
Definition: background radiation (also called
naturally occurring nuclear radiation) occurs
naturally in the environment
When nuclear radiation exceeds background
levels, it can damage cells and tissues
Nuclear radiation can ionize atoms including
alpha, beta and gamma
Alpha can burn skin but is not serious
unless inhaled or eaten (ex: radon gas in
homes)
Beta does more damage than alpha, but less
than gamma
Gamma rays cause extensive damage
Devices
that are used to detect
nuclear radiation include geiger
counters & film badges
Film badges are worn by people
who work with radiation to detect
excessive levels
Objectives:
1.
Define half-life and relate halflife to the age of radioactive
isotope
2. Compare and contrast nuclear
reaction rates with chemical
reaction rates
3. Describe how radioisotopes are
used to estimate the age of
materials
Definition: half-life is the time required
for one half of a sample of a
radioisotope to decay
Half life = total time of decay/half-life
Q: If a radioactive sample has decayed
until one eighth of the original sample
remains, how many HL have elapsed?
A: three HL ( ½ x ½ x ½ = 1/8 )
Nuclear decay rates are constant
regardless of temperature, pressure or
surface area of the reactant (ex:
uranium-238)
Chemical reactions are affected by local
conditions (temp, press, surface area,
etc.)
Carbon-14 has an unstable nucleus
and is radioactive
It can be used to determine the age
of an object by comparing the
object’s carbon-14 levels with the
carbon-14 levels in the atmosphere
146C --> 147N + 0-1e (half-life is 5720
years)
Any object can be dated that is less
than 50,000 years old
Older objects contain too little
carbon to be useful
Objectives:
1.
Explain what a particle
accelerator is
2. Describe the process of nuclear
fission
3. Explain how nuclear reactors
are used to produce energy
4. Describe the process of nuclear
fusion
Definition: transmutation is
conversion of atoms of one element
into atoms of another element
Scientists can bombard atomic nuclei
with high energy protons, neutrons
or alpha particles creating a new
element
The equipment used to do this is
called a particle accelerator
An important accelerator is located in
Illinois
Definition: fission is the splitting of an
atomic nucleus into two smaller parts
Tremendous amounts of energy can
be produced from very small amounts
of mass by creating a chain reaction
Definition: a chain reaction produces a
series of nuclear reactions by
releasing neutrons off an initial
nuclear trigger
Speed of the reaction can vary
Controlled reactions can be used to
produce electricity
Definition: critical mass is the smallest
possible mass of fissionable material
that can sustain a chain reaction
The fissionable material in the United
States is radioactive uranium-235
Electricity production with controlled
fission takes place at nuclear power
plants
There are not many out West, although
some politicians are trying to change
that
Currently, the majority of nuclear power
plants are located East of Nevada
Nuclear power plants do not emit air
pollutants unlike power plants that
burn fossil fuels
Workers in nuclear plants must wear
protective clothing reducing
exposure to radiation
The uranium-235 produces many
radioactive isotopes
The waste must be stored for
hundreds of half-lives or thousands
of years
The waste must be isolated from
humans & the environment
Operators have lost control of the
reactor from time to time
During a nuclear core meltdown the
core melts and radioactive material
can be released
A partial meltdown happened in
1986 in Chernobyl, Ukraine
Chernobyl will be uninhabitable for
many generations to come
It came to close to happening at
Three Mile Island, Pennsylvania
Definition: fusion is the process in
which the nuclei of two atoms combine
to form a larger nucleus
A fraction of the reactant is converted
to energy during this process but we do
not yet have the technology to harness
the energy & convert it to electricity
Fusion requires the temperature of the
sun in excess of 10 million degrees
Definition: plasma is a state of matter
in which atoms have been stripped of
their electrons
Fusion reactors do not yet exist due to
the temperatures required to start the
reaction & they must contain plasma