Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
252 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 24
24.4 Fission and Fusion of Atomic Nuclei
Albert Einstein’s most famous equation relates mass and energy.
⌬E ϭ ⌬mc 2
In the equation, ⌬E is change in energy (joules), ⌬m is change in
mass (kg), and c is the speed of light (3.00 ϫ 10 8 m/s). The equation
indicates that a loss or gain in mass accompanies all chemical and
nuclear reactions that produce or consume energy. Although the
energy and mass changes in chemical reactions are negligible, those
that accompany nuclear reactions are significant.
The energy released when an atom’s nucleons bind together is
called binding energy. The greater the binding energy, the more stable a nucleus is. Elements with a mass number near 60 are the most
stable.
The mass of a nucleus is actually less than the sum of the
masses of the nucleons. This difference is called the mass defect.
The missing mass in the nucleus provides the energy that holds a
nucleus together.
Nuclear fission Heavy atoms (mass number Ͼ 60) tend to break
into smaller atoms, thereby increasing their stability. The splitting of
a nucleus into fragments is called nuclear fission. Nuclear fission
releases a large amount of energy.
One fission reaction can lead to more fission reactions, a process
called a chain reaction. A chain reaction can occur only if the starting material has enough mass to sustain a chain reaction; this
amount is called critical mass. With a subcritical mass, the chain
reaction stops or never begins. With a supercritical mass, the chain
reaction accelerates and can lead to a violent explosion.
Nuclear reactors Nuclear power plants use the process of
nuclear fission to produce heat in nuclear reactors. The heat is used
to generate steam, which is then used to drive turbines that produce
electricity. Fissionable uranium(IV) oxide (UO 2 ) is commonly used
as fuel in nuclear reactors. Cadmium and boron are used to keep the
fission process under control. Continual adjustments are needed to
keep the reaction going and under control.
▲
▲
252 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 24
24.4 Fission and Fusion of Atomic Nuclei
Albert Einstein’s most famous equation relates mass and energy.
⌬E ϭ ⌬mc 2
In the equation, ⌬E is change in energy (joules), ⌬m is change in
mass (kg), and c is the speed of light (3.00 ϫ 10 8 m/s). The equation
indicates that a loss or gain in mass accompanies all chemical and
nuclear reactions that produce or consume energy. Although the
energy and mass changes in chemical reactions are negligible, those
that accompany nuclear reactions are significant.
The energy released when an atom’s nucleons bind together is
called binding energy. The greater the binding energy, the more stable a nucleus is. Elements with a mass number near 60 are the most
stable.
The mass of a nucleus is actually less than the sum of the
masses of the nucleons. This difference is called the mass defect.
The missing mass in the nucleus provides the energy that holds a
nucleus together.
Nuclear fission Heavy atoms (mass number Ͼ 60) tend to break
into smaller atoms, thereby increasing their stability. The splitting of
a nucleus into fragments is called nuclear fission. Nuclear fission
releases a large amount of energy.
One fission reaction can lead to more fission reactions, a process
called a chain reaction. A chain reaction can occur only if the starting material has enough mass to sustain a chain reaction; this
amount is called critical mass. With a subcritical mass, the chain
reaction stops or never begins. With a supercritical mass, the chain
reaction accelerates and can lead to a violent explosion.
Nuclear reactors Nuclear power plants use the process of
nuclear fission to produce heat in nuclear reactors. The heat is used
to generate steam, which is then used to drive turbines that produce
electricity. Fissionable uranium(IV) oxide (UO 2 ) is commonly used
as fuel in nuclear reactors. Cadmium and boron are used to keep the
fission process under control. Continual adjustments are needed to
keep the reaction going and under control.
▲
▲