Nuclear
Chemistry
ALPHA-Chemistry I-B
Chapter 28
Wilhelm Roentgen
• Wilhelm Roentgen
• Discovered X-rays
• Was awarded a
Nobel Prize for the
discovery of the
mysterious rays
Henri Becquerel
• Henri Becquerel was a
part of the group that
made a the early
discoveries of
radiation.
Marie Curie
• Marie Curie and her
husband made the
discovery of
radiation.
• She was awarded
two Nobel Prizes for
her work.
The Discovery of Radiation
• Henri Becquerel (1895) discovered that
pitchblend (Uranium ore) would expose
film. He called it radioactivity.
• Marie and Pierre Curie worked long
difficult hours and discovered new
elements-Radium and Polonium
Nuclear vs. Ordinary Reactions
• Ordinary chemical changes (the ones
that display our indicators of chemical
reactions) only involve electrons.
• Nuclear changes involve the nucleus and
create new atoms.
– Larger atoms are from fusion
– Smaller atoms are from fission
Radiation
• Radioactivity or Radiation is the
spontaneous emission of alpha, beta, or
gamma rays the disintegration of the
nuclei of atoms.
Types of Radiation
• Alpha particles
– A helium atom doesn’t have any electrons; positively
charged.
• Beta Particles
– A very fast moving electron
– Negatively charged
• Gamma Rays
– A form of energy lots of energy that moves in waves
– The rays go through a lot of materials.
Going for the Block
• Alpha particles can be blocked by a piece
of paper; however, once inside the body
the most immediate damage.
• Beta particles can be stopped with a
piece of Al foil. They do more damage
over a great area of the body.
• Gamma rays penetrate most things and
do the most damage to DNA.
Radiation Protection
1. Distance
2. Time
3. Shielding
Nuclear Protective Gear
Nuclear Equations-Know your
particles and all is easy
4
• Alpha particles -changes • Alpha Particle
2
the mass number by four
and the atomic number
0
by two. It’s a Helium • Beta Particle
1
nucleus
• Beta Particles -changes
1
the atomic number by
• Neutron
0
one. No change to the
mass number.
• Neutron -no change to
the mass number, but the
mass changes by one.
These are the main ones !!!!!!
He
e
n
The other particles
• Proton
• Positron
1
1
H
0
1
e
Five types of nuclear change
1.
2.
3.
4.
5.
Alpha Decay
Beta Decay
Gamma Decay
Fission (spitting)
Fusion (joining)
Nuclear Equations
• Both sides of the equation must be equal
in both mass number and atomic
number!
• It’s just very easy algebra!
Examples:
10
5
B  n  He  ?
39
19
1
0
K  n 
1
0
4
2
36
17
Cl  ?
Word Problem Example
• Thorium-225 undergoes alpha decay.
Write a balanced equation for the
reaction.
Decay Series
• A continuous flow of
nuclear decay.
Fission reaction
• Nuclear fission is when nucleus is split
into two smaller nuclei.
Fusion
• Fusion is when two nuclei join to form a
larger nucleus. The same reaction occurs
in the sun!
A Fission Reactor
• Cannot explode like a nuclear bomb.
Uses a different form of uranium-238
• There is actually less pollution that goes
into the air.
• Nuclear weapons use uranium-235
Half-Life
• Half life is defined as the time it takes for one
half the mass of the radioactive isotope to
become stable (non-radioactive)
• Substances with short half-lives can cause
more health hazards than isotopes with long
half-lives (radiation is given off much more
slowly.)
• We are going to view an animation:
• http://library.thinkquest.org/27948/decay.html
Half-Life Terms
• The portion that remains radioactive is
called the parent
• The decayed portion is called the
daughter.
• The daughter is not usually radioactive,
but it can be.
Examples
• Carbon-14 has a half-life of 5700 years.
How much remains of a 600 gram
sample after 17,100 years?
• Polonium-210 has a half-life of 138.4
days. How much remains of a 1000 gram
sample after 98.86 weeks.
Calculating half-life
•
•
The fraction of the original amount that
remains is still radioactive.
The easy way:
1. Determine the number of half-lives
2. Divide the mass by 2 until you have
divided as many times as you have
number of half-lives
– The Formula: 1
2
n
( mass of substance)  amt. left
Carbon Dating
Carbon-14 and Nitrogen-14 are used to
date items based on the half-life of
carbon-14.
We know it takes 5730 years to decay
carbon-14.
The amount present in the atmosphere is
constant. So you just measure what’s in
the artifact and work backwards.
Measuring Radiation-read only
• Rad=Radiation Dose
• Rankin=rad/hour
• REM=roentgen equivalent man
– 1/1000 rem = 1 mrem
• LET=Linear energy transfer
• A rad is the amount of energy that is released
in tissue when it is irradiated. One rad=100
ergs (energy uints) deposited in one gram of
tissue.
REM-read only
• A REM measures the biological effect of
radiation on the human body without
having to worry about the type of
radiation involved.
• What’s allowed? 5-10 rems per year. It’s
very rare
When radiation hits a cell-read
only
• It may pass through the cell w/o damage.
• It may damage the cell, but the cell fixes
the damage.
• It may damage the cell; the cell
reproduces the damaged form.
• The cell dies-serious problems occur if
too many cells are killed in a certain
organ.
Guidelines-read only
• From WWII Studies:
– 650 rads
– 300 rads
– 50-250 rads
Death within a few
hours
Lethal-death in 60 days
Radiation sickness
• Symptoms of radiation sickness
– Nausea, vomiting, diarrhea, hair loss,
sore throat, reduction in blood platelets,
bone marrow damage
– Delayed effects: Cancer, leukemia,
cataracts, sterility, decreased lifespan