nuclear chemistry only one element has unique names for its isotopes … deuterium and tritium are...
TRANSCRIPT
Only one element has unique names for its isotopes …
tritium H
deuterium H
hydrogen H
31
21
11
Deuterium and tritium are used in nuclear reactors and fusion research.
Some isotopes are radioactive
Radioactive isotopes are called radioisotopes.
Radioisotopes can emit alpha, beta or gamma
radiation as they decay.
Man-made Isotopes
Cobalt-59 occurs naturally. When a neutron “sticks” to the nucleus,
cobalt-60 is formed.
Man-made isotopes are usually made by bombarding atoms with protons or neutrons.
Uses for Isotopes
Radioisotopes are used as tracers in chemical reactions.
Radioisotopes are used in “imaging” living and nonliving systems.
Radioisotopes are used to kill cancer cells. (Co-60, Bi-212)
Mass number /Atomic number
U235
92
Mass number
Symbol of Element
Atomic number
protons + neutrons
Protons in nucleus
Mass number
Alpha () particles are the nuclei of helium atoms and have the symbol 2He4.
What is the atomic number
of an particle?2 He4
Alpha () particles are the nuclei of helium atoms and have the symbol 2He4.
How many times heavier is an alpha particle than
a hydrogen atom?4
Beta () particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1e0.What is the mass number of a particle?
-1e0
Beta () particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1e0.
No protons or neutrons in an electron. -1e0
Beta () particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1e0.
NoneWhat is the difference between a particle and a “regular” electron?
Beta () particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1e0.
LocationLocationLocation
What is the difference between a particle and a “regular” electron?
Gamma () rays are high energy electromagnetic waves, not particles.
No protons, neutrons or electrons.
Gamma rays have short wavelengths and high energies and travel at the speed of light.
Alpha, Beta, Gamma
Radioactive Source
- - - - - - - - -
+ + + + + + + +
Electric field from electrically charged plates
What is the effect of an electric field on
Alpha, Beta, Gamma
Radioactive Source
- - - - - - - - -
+ + + + + + + +
Electric field from electrically charged plates
Alpha, Beta, Gamma
Radioactive Source
- - - - - - - - -
+ + + + + + + +
Are , and rays deflected by magnetic fields?
Electric field from electrically charged plates
Radiation Project
Create a table listing information for each of the three kinds of radiation:
Alpha, beta and gamma
Properties to include in your table:
(1) Greek letter
(2) symbol
(3) actually is
(4) atomic number
(5) mass number
(6) relative mass
(7) relative. charge
(8) penetrating ability
(9) shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter
Symbol
Actually is…
Atomic number
Mass number
Relative mass
Relative charge
Penetrating
Shielding
Stop!Complete the chart on notebook paper,
then continue.
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter
Symbol
Actually is…
Atomic number
Mass number
Relative mass
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
Actually is…
Atomic number
Mass number
Relative mass
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is…
Atomic number
Mass number
Relative mass
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number
Mass number
Relative mass
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number 2 -1 NA
Mass number
Relative mass
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number 2 -1 NA
Mass number 4 0 NA
Relative mass
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number 2 -1 NA
Mass number 4 0 NA
Relative mass 4 1/1837NA
Relative charge
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number 2 -1 NA
Mass number 4 0 NA
Relative mass 4 1/1837NA
Relative charge +2 -1 NA
Penetrating
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number 2 -1 NA
Mass number 4 0 NA
Relative mass 4 1/1837NA
Relative charge +2 -1 NA
Penetrating Low Medium High
Shielding
Nuclear Properties TableProperty Alpha Beta Gamma
Greek Letter Symbol
2He4-1e0 NA
Actually is… He nucleus electron EM energy
Atomic number 2 -1 NA
Mass number 4 0 NA
Relative mass 4 1/1837NA
Relative charge +2 -1 NA
Penetrating Low Medium High
Shielding 2.5 cm of air;anything else
Metal, plastic or wood
Lead or concrete
Protection from radiation1. Shielding 2. Distance
How do you protect yourself from …
Alpha
Beta
Gamma
2.5 cm of air, paper, skinaluminum, lead, other metals, wood, plastic, etc.up to a foot or two of lead, many feet of concrete
Gamma rays and high energy cosmic particles from space.
But there is one kind of radiation hazard that you
can protect against.
Radiation
Uranium-238 decays through
many steps to make stable
lead-206
The uranium decay series
http://library.tedankara.k12.tr/chemistry/vol1/nucchem/trans90.htm
The uranium decay series
Radon is the only gas in the series.
http://library.tedankara.k12.tr/chemistry/vol1/nucchem/trans90.htm
Hazards from radon
Since radon is the only gas in the decay series of uranium …
…it can work its way up through the ground and into your
basements and crawl spaces.
You breathe radon into your lungs.
Hazards from radon
And when radon is in your lungs…
…it can decay and release an alpha particle …
…which travels only a short distance before it is absorbed by your lungs, and transfers its energy.
Hazards from radon
This ionizing radiation in your lungs can cause lung cancer.
Smoking cigarettes and breathing radon really increases your
chances of getting lung cancer.
Protecting against radon
Get a test kit to see if there is a problem. Charcoal canisters, which are sent off for analysis.
Abatement:Seal places where gas gets in.
Ventilation – bring in fresh air.
What is half life?
Half life is the time needed for one half of a radioisotope to decay.
Suppose you start with 100.0 grams of a radioisotope that has a half life
of exactly 1 year.
What is half life?
How much will be left after 1 year?
Suppose you start with 100.0 grams of a radioisotope that has a half life
of exactly 1 year.
What is half life?
After one year there will be 50.0 g left.
Suppose you start with 100.0 grams of a radioisotope that has a half life
of exactly 1 year.
After a second year there will be 25.0 g left.
What is half life?
After a third year there will be 12.5 grams left.
After one year there will be 50.0 g left. After a second year there will be
25.0 g left.
After a fourth year there will be 6.25 grams left.
Half life project1. Pick a mass between 10g and 50g. 2. Decide on a half life – any time.3. Scale your graph – mass on y-axis
and at least six (6) half-lives on the x-axis.
4. Plot the masses after intervals of one half-life.
Half life project5. What shape is the graph?6. When will the mass of the
radioisotope fall to zero?7. When is the radioactivity no
longer a problem? 8. What mathematical function
describes radioactive decay?
Half life projectA
ctiv
ity
(cou
nts/
min
)
Time (min)
200
10050
t1/2 t1/2
Exponential decay
A = A0e-kt
Half life project
Time (min)
10050
t1/2 t1/2A
ctiv
ity
(cou
nts/
min
)
background
Radiation is “not a problem” when it falls below background level.
200
Half life projectQuestions:
1. A radioisotope has a half-life of 100 years. How long will it take for the radiation to decrease to 1/16 of its original value?
400 years
Half life projectQuestions:
2. A radioisotope has an activity of 560 counts per minute. After 16 hours the count rate has dropped to 35 counts per minute. What is the half life of the radioisotope?
4 hours
Alpha decay
In alpha decay, an alpha particle (2He4) is released from the nucleus.
The alpha particle carries away two protons and two neutrons.
Alpha decay
86Rn220 2He4 + ???
Radon-220 decays by alpha emission. What is the decay product?
84Po216
Alpha decay
Write the alpha decay equations for:
1. 95Am241
2. 84Po216
3. 88Ra226
2He4 + 93Np237
2He4 + 82Pb212
2He4 + 86Rn222
Beta decay
Neutrons are a little more massive than protons; neutrons are neutral.
What does this suggest about the composition of neutrons?
Beta decay occurs because of the instability of a neutron.
Beta decayScientists used to think that neutrons might be a combination of a proton and an electron.
We know that neutrons decay into protons, which stay in the nucleus,
and electrons, which are ejected from the nucleus as beta particles.
Beta decay
0n1 1H1 + -1e0
neutron proton electron
The electron ejected from the nucleus is a beta particle.
Decay of a neutron:
Beta decay
0n1 1H1 + -1e0 + 00
neutron proton electron
Technically, the decay of a neutron also involves a neutrino.
anti-neutrino
Beta decay
0n1 1H1 + -1e0 + 00
neutron proton electron
Actually, an anti-neutrino.
anti-neutrino
The word “neutrino” comes from Enrico Fermi, meaning “little neutral one” in Italian.
Beta decay
0n1 1H1 + -1e0 + 00
neutron proton electron
A neutrino is a particle with no charge and almost no mass.
anti-neutrino
Beta decay
0n1 1H1 + -1e0 + 00
neutron proton electron
A neutrino carries off some of the energy in the decay of the neutron.
anti-neutrino
Beta decay
0n1 1H1 + -1e0 + 00
neutron proton electron
When predicting the products of beta decay we will ignore neutrinos.
anti-neutrino
Beta decayStart with a Li atom with
3 protons and 4 neutrons.
Suddenly a neutron decays!
Now there are 4 protons
and 3 neutrons.
A beta particle goes zipping out of
the nucleus.
Beta decay
The number of neutrons
The number of protons
The mass number
The atomic number
A neutron decays to make a proton.
decreases by 1
increases by 1
stays the same.
increases by 1
Beta decay
Write the beta decay equations for:
1. 82Pb214
2. 27Co62
-1e0 + 83Bi214
-1e0 + 28Ni62
3. ??? -1e0 + 48Cd11347Ag113
Review: decay equationsAlpha:
Go down two on periodic tableAtomic number decreases by 2Mass number decreases by 4
Beta:Go up one on periodic tableAtomic number increases by 1Mass number stays the same
Nuclear energy
All have enough energy to ionize atoms.
Gamma rays are electromagnetic energy.
Alpha and beta particles have high kinetic energies.
All nuclear decay is accompanied by a release of energy.
Nuclear energy
This can result in damage to your body.
Ionization occurs when electrons are removed from
atoms by or radiation.
An ion is a “charged atom” or group of atoms.
cancer