Nuclear
Chemistry
September 21, 2009
Trianna McCall
Nuclear Reactions
• Nuclear chemistry is the study of
changes in an atoms nucleus.
• Reactions that involve a change in
the nucleus of an atom are called
nuclear reactions.
Characteristics of Nuclear
Reactions
• Occur when nuclei emit particles and/or rays
• Atoms are often converted into atoms of
another element
• May involve protons, neutrons, and electrons
• Associated with large energy changes
• Reaction rates aren’t normally affected by
temperature, pressure, or catalyst
Table 25-1 (p805 of textbook)
What Causes Nuclear Reactions?
• The nuclei of some atoms are
unstable and may undergo several
changes.
• Unstable systems gain stability by
losing energy.
• Certain atoms lose energy by
emitting rays and particles called
radiation.
Related Terms
• This spontaneous emission of radiation is
a process called radioactivity.
• The process by which unstable nuclei
emit radiation to lose energy is called
radioactive decay.
• Radioisotopes, isotopes of atoms with
unstable nuclei, undergo nuclear decay.
Types of Radiation
• Alpha
-Composed of alpha particles
-Contains 2p+ and 2n⁰
-42He
• Beta
-Composed of beta particles
-Fast moving e- 0-1β or 0-1e
Types of Radiation (cont)
• Gamma
-Not deflected by electric or magnetic
fields
-No charge
-00γ
• http://www.mhhe.com/physsci/chemistry/ess
entialchemistry/flash/radioa7.swf
Types of Radiation Summary
Type of
Radiation
Symbol
Charge
Penetration
Ability
Mass
alpha
4
2He
2+
blocked by
paper
heaviest
(4 amu)
beta
0
-1β
1-
blocked by
metal foil
lightest
(1/1840 amu)
gamma
0
0γ
0
not completely none
blocked by lead
or concrete
Nuclear Equations
• Used to express nuclear reactions
• Both sides of the equation must have an equal
sum of atomic mass and atomic numbers
• Examples:
- 23592U  ______________ + 23190Th
- 37K  0e + ______________
- 41Ca  Ca + 0 _________________
Half-Life
• The time required for one half of a
radioisotope’s nuclei to decay into its products
is called a half-life.
• Amt Remaining=(Initial Amt)(1/2)n
-n = # half lives passed
• Amt Remaining=(Initial Amt)(1/2)t/T
-t=elapsed time
-T=duration of half life
Half-Life (cont)
• Example half-life problems:
- How much of a 100.0g sample of 198Au is
left after 8.10 days if its half-life is 2.70 days?
-A 50.0g sample of 16N decays to 12.5g in
14.4 seconds. What is its half-life?
-The half-life of 42K is 12.4hours. How
much of a 750g sample is left after 62.0hours?
-What is the half-life of 99Tc if a 500g
sample decays to 62.5 g in 639,000 years?
Fission and Fusion
• The splitting of an atoms nucleus into
fragments is called fission.
-Provides energy for nuclear power plants
• http://www.visionlearning.com/library/flash_
viewer.php?oid=2391&mid=59
• The combining of atomic nuclei is called
fusion.
-Fuels the sun
• http://www.visionlearning.com/library/flash_
viewer.php?oid=2747&mid=59