Radioactivity
and Nuclear
Chemistry
“Nuclear energy is incomparably greater than the molecular energy which
we use today ... What is lacking is the match to set the bonfire alight ...
The scientists are looking for this.
Winston Spencer Churchill (in 1934)
Deborah C. Koeck, Southwest Texas State University
Prentice Hall ©2003
Radioactivity and Nuclear Chemistry
Diagnosing Appendicitis
• Radioactivity
– Emission of Tiny,
Invisible Particles
• Tagged Antibodies
– Naturally Occurring
Molecules Marked with
Radioactive Molecules
• Diagnosis
Radioactivity and Nuclear Chemistry
The Discovery of Radioactivity
• Becquerel
(1852–1908)
– Discovered
Radioactivity
• Phosphorescence
– Long-lived Emission of
Light
• Experiment
Radioactivity and Nuclear Chemistry
The Discovery of Radioactivity
• Curie (1867–1934)
• Radioactivity
• Nobel Prize
Radioactivity and Nuclear Chemistry
Types of Radioactivity:
Alpha, Beta, and Gamma Decay
• Characterization of Radioactivity
• Isotopes
• Protons, Neutrons, and Electrons
Radioactivity and Nuclear Chemistry
Types of Radioactivity:
Alpha, Beta, and Gamma Decay
Radioactivity and Nuclear Chemistry
Alpha Radiation
• Alpha particles are nuclear decay particles.
– Unstable Nucleus Emits a Small Piece of
Itself
– They consist of two protons and two
neutrons
• Alpha Particle – symbol = 
– Helium Nucleus
• The particles are expelled from a nucleus
at a fairly low speed, approximately onetenth the speed of light.
• They are a minimal health risk to people
unless ingested or inhaled.
• The large mass nuclei tend to use alpha
emission because it is a quick way for a
large mass atom to lose a lot of nucleons.
4
2
He
Radioactivity and Nuclear Chemistry
• Nuclear Equation
– Sum of the atomic numbers on both sides of a
nuclear equation must be equal
– Sum of the mass numbers on both sides of a
nuclear equation must be equal
Radioactivity and Nuclear Chemistry
Alpha Radiation
• Alpha Radiation
–
–
–
–
High Ionizing Power
Low Penetrating Power
2 Protons
2 Neutrons
Radioactivity and Nuclear Chemistry
Beta Radiation
0
• Beta Radiation – symbol:  or -1 e
– Beta Emission is a nuclear
decay process. It is the
process that ejects a high
speed electron from an
unstable nucleus.
– The electron is formed on the
spot within the nucleus by the
breakdown of a neutron into a
proton and electron.
14
6
C
14
7
0
1
N+ e
Radioactivity and Nuclear Chemistry
0
Beta Radiation -1 e
– The electron is released from the system.
– The proton that was formed remains behind in the
nucleus.
– As a result of the addition of the proton, the atomic
number of an element increases during beta
emission.
– Beta emission can be a significant health risk.
Radioactivity and Nuclear Chemistry
Gamma Decay
• Gamma Radiation – symbol: 
– Gamma Emission occurs primarily after the emission of a decay particle.
– Gamma is a form of high energy electromagnetic radiation.
– After a particle is ejected from a nucleus the system may have some
slight excess of energy, or exist in a meta-stable state. This slight excess
of energy is released as gamma.
– Gamma emission will not change the isotope or the element. The
wavelength of the emitted gamma radiation will be be unique to each
isotope.
– Gamma emission is a significant health risk.
– No Mass
– No Charge
Radioactivity and Nuclear Chemistry
Alpha, Beta and Gamma Decay
Separation
Note the behavior of the different radiation through a magnetic field: Alpha
particles are positive helium nuclei, so they are deflected towards the negative
plate, Beta are high speed electrons so they are attracted to the positive plate.
Gamma radiation is completely unaffected by the magnetic field.
Radioactivity and Nuclear Chemistry
Types of Radioactivity: Positron Emission
• Positron Emission
– Unstable Nucleus
Emits a Positron
– Positron has the Mass
of the Electron
– Charge is +1
0
+1
e
Radioactivity and Nuclear Chemistry
Natural Radioactivity and Half-Life
• Radioactivity is a Natural
Environmental Component
– Earth’s Surface Contains
Radioactivity
– Radiation in Space
– Food Contains Residual
Radiation
• Half-Life
– Time for One Half of the
Parent Nuclides to Decay
to Daughter Nuclides
Radioactivity and Nuclear Chemistry
Natural Radioactivity and Half-Life
• Radon has a half-life of 3.8 days.
Given a 96.0 gram sample, how
many grams will remain after 19
days?
Answer: 3.0 grams remain
Radioactivity and Nuclear Chemistry
Natural Radioactivity and Half-Life
• Natural Radioactive
Decay Series
Radioactivity and Nuclear Chemistry
Detecting Radioactivity
• Film-badge Dosimeter
– Photographic Film
– More Exposed the Film 
More Exposure to
Radioactivity
• Geiger-Müller Counter
– Radioactive Particles
– Create a Trail or Electrical
Signal
Radioactivity and Nuclear Chemistry
Radiocarbon Dating
• Radiocarbon Dating
• Carbon-14
• Shroud of Turin
– Burial Cloth of Jesus
Christ
– Dated at 1325 A.D.
Radioactivity and Nuclear Chemistry
The Discovery of Fission and the Atomic Bomb
• Fermi (1901–1954)
• Nuclear Fission – 1939
– Meitner, Strassmann, and Hahn
Radioactivity and Nuclear Chemistry
The Discovery of Fission and the Atomic Bomb
•
•
•
•
•
Chain Reaction
Fission is the process known as "splitting the
atom."
During fission, a large mass nucleus is split into two
or more smaller mass nuclei.
During the process large quantities of energy are
released as the products.
Fission is the currently used process for the
production of nuclear energy.
Radioactivity and Nuclear Chemistry
Radioactivity and Nuclear Chemistry
Nuclear Power: Using Fission to Generate Electricity
• Nuclear Reactors
• Generate Energy
– 20% of U.S. Energy
Generated by
Fission
– Energy Released
Slowly
Radioactivity and Nuclear Chemistry
Nuclear Fusion: The Power of the Sun
• Nuclear Fusion
– Powers the Sun and Stars
– Fusion is the process that unites
small mass nuclei into a larger
mass nucleus.
– During fusion extremely large
quantities of energy are released.
This is a much more efficient
process than fission.
– It produces considerably more
energy that fission.
Unfortunately, it is very difficult
to accomplish and is not being
utilized as a source of energy by
society.
• Generate Energy
– Deuterium
– Tritium
Radioactivity and Nuclear Chemistry
Nuclear Fusion: The Power of the Sun
Radioactivity and Nuclear Chemistry
The Effects of Radiation on Life
•
•
•
•
Acute Radiation Damage
Increased Cancer Risk
Genetic Defects
Measuring Radiation Exposure
– Radiation used to be measured in rads and rems however these
units have been changed to fit within the International System
of Measurement and is now measured grays, Gy.
– One gray is equal to the transfer of one joule of energy to one
kilogram of living tissue. One gray is a unit of absorbed
radiation dose equal to 100 rads.
– The damage to tissue is better indicated by the absorbed dose
of radiation, which is measured in sieverts, Sv. A sievert is
equal to a gray multiplied by factors that determine how much
of the energy transferred was actually absorbed by the tissue.
Radioactivity and Nuclear Chemistry
Measuring Radiation Exposure
• We are always being exposed to radiation found naturally in our
environment. This radiation is known as background radiation
and is equal to about 0.001 Sv/year. Here is a general idea about
radiation amounts:
• A single medical X-ray produces about 0.2 mSv (0.0002 Sv)
• Nuclear reactor workers are permitted to receive up to 0.05
Sv/year
• An exposure of 1 Sv/hour results in radiation poisoning
• Exposure to 3 to 5 Sv/hour results in death in 50% of the cases
Radioactivity and Nuclear Chemistry
Radioactivity in Medicine
• Isotope Scanning
• Radiotherapy
– Cancer Therapy
Radioactivity and Nuclear Chemistry
Chemical Principles
•
•
•
•
•
•
The Nature and Discovery of Radioactivity
Detecting Radioactivity
Half-Life and Radiocarbon Dating
Fission, the Atomic Bomb, and Nuclear Power
Nuclear Fission
The Effects of Radiation on Life and Nuclear
Medicine
Radioactivity and Nuclear Chemistry
Chemical Skills
• Writing Nuclear Equations for Alpha Decay
• Writing Nuclear Equations for Beta Decay
• Identifying the degree of penetration by the different
types of nuclear decay
• Using Half-Life
• Using Carbon-14 Content to Determine the Age of
Fossils or Artifacts