intro to nuclear chemistry powerpoint basics from mrs. coyle and other internet sources
TRANSCRIPT
Intro to Nuclear Chemistry
http://www.chem.orst.edu/graduate/pics/Reactor.jpgPowerPoint basics from Mrs. Coyle and other Internet Sources
Learning Objectives
• TLW understand the basic process of nuclear chemistry (TEKS 12)– TLW be able to describe alpha, beta, and
gamma radiation (TEKS 12.A)– TLW describe radioactive decay process in
terms of balanced nuclear equations (TEKS 12.B)
– TLW compare fission and fusion reactions (TEKS 12.C)
Anticipatory Exercise
• Background Radiation – What’s YOUR Exposure?– Flinn Scientific ChemTopicTM Labs – Book 18,
page 2
How does a nuclear reactor work?
http://www.lanl.gov/science/1663/images/reactor.jpg
How does a small mass contained in this bomb cause……
• Nuclear Bomb of 1945 known as “fat man”
http://www.travisairmuseum.org/assets/images/fatman.jpg
…this huge nuclear explosion?
http://library.thinkquest.org/06aug/01200/Graphics/705px-Nuclear_fireball.jpg
Is there radon in your basement?
http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg
Nuclear Notation
Practice Using Nuclear Notation
• How would you write the following elements using nuclear notation?
H
C
Co
U
Nucleons
• Protons and Neutrons
• The nucleons are bound together by the strong force.
Isotopes
• Atoms of a given element with:
same #protons
but
different # neutrons
H H H
http://education.jlab.org/glossary/isotope.html
Isotopes of Carbon
• Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus.
• Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film.
• His associates were Marie and Pierre Curie.
Radioactive Isotopes
Marie Curie: 1867 - 1934, in Poland as Maria Sklodowska
• Lived in France
• 1898 discovered the elements polonium and radium.
http://www.radiochemistry.org/nuclearmedicine/pioneers/images/mariecurie.jpg
Marie Curie a Pioneer of Radioactivity
• Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie (1859 – 1906)
• Winner of the sole 1911 Nobel Prize for Chemistry
• Sadly, she and Pierre died of radiation poisoning
General Nuclear Equations
• Handout of Graphic Organizer on General Nuclear Equations
3 Main Types of Radioactive Decay
• Alpha
• Beta
• Gamma
Emission of alpha particles :
• helium nuclei • two protons and two neutrons • charge +2e • can travel a few inches through air• can be stopped by a sheet of
paper, clothing.
Alpha Decay
Alpha Decay
Uranium Thorium alpha particle
Alpha Decay
http://education.jlab.org/glossary/alphadecay.gif
Beta Decay
• Beta particles : electrons ejected from the nucleus when neutrons decay
( no p+ +- )
• Beta particles have the same charge and mass as "normal" electrons.
Beta Decay
• Beta particles : electrons ejected from the nucleus when neutrons decay
no p+ +-
• Beta particles have the same charge and
mass as "normal" electrons.
• Can be stopped by aluminum foil or a block of wood.
Beta Decay
Beta Decay
Thorium Protactinium beta particle
• Gamma radiation electromagnetic energy that is released.
• Gamma rays are electromagnetic waves.
• They have no mass.• Gamma radiation has no charge.
– Most Penetrating, can be stopped by 1 m thick concrete or a several cm thick sheet of lead.
Gamma Decay
Examples of Radioactive DecayAlpha Decay
Po Pb + He
Beta Decay p n + e
n p + e
C N + e
Gamma Decay
Ni Ni + (excited nucleus)
Which is more penetrating & potentially more harmful? Why?
Second Graphic Organizer
• Nuclear Decay Organizer (pdf) - link
Part II
•Balancing Nuclear Equations
Balancing Nuclear ReactionsBalancing Nuclear Reactions•In the reactants (starting materials – on the left side of an equation) and products (final products – on the right side of an equation) – Law of Conservation of Mass
Atomic numbers must balanceand
Mass numbers must balance
•Use a particle or isotope to fill in the missing protons and neutrons
Nuclear ReactionsNuclear Reactions
• Alpha emissionAlpha emission
Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2.Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved
Nuclear ReactionsNuclear Reactions
• Beta emissionBeta emission
Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.
Other Types of Nuclear Other Types of Nuclear ReactionsReactions
Positron (Positron (00+1+1): a positive electron): a positive electron
Electron capture: Electron capture: the capture of an electron
207 207
Learning Check
What radioactive isotope is produced in the following bombardment of boron?
10B + 4He ? + 1n
5 2 0
Write Nuclear Equations!
Write the nuclear equation for the beta emitter Co-60.
Group Practice
• Work some problems together using ELMO
• See Nuclear Equations Worksheet – page 4 of Flinn ChemTopicTM Labs book (vol. 18)
Independent Practice Set
• Balancing Nuclear Equations – 1
• Balancing Nuclear Equations – 2 (Word Problems)
Part III
•Nuclear Stability
•Half-Life
Introduce Half-Life with Lab
• Half-Life of M&Ms (TAMU handout) or
• Half-Life of Licorice (TAMU Handout) or
• Half-Life with Pennies– IPC Lab Manual – pages 152 & 153
Nuclear Stability
• Depends on the neutron to proton ratio.
Band of Stability
Number of Neutrons, (N)
Number of Protons (Z)
What happens to an unstable nucleus?
• They will undergo decay
• The type of decay depends on the reason for the instability
What type of decay will happen if the nucleus contains too many neutrons?
• Beta Decay
Example:
C N + e
In N-14 the ratio of neutrons to protons is 1:1
14
7 -1
014
6
• Nuclei with atomic number > 83 (Bismuth) are radioactive
Radioactive Half-Life (t1/2 ):
• Through study of radioactive isotopes, scientists have defined the rate of instability as half-life
• In other words…. The time for half of the radioactive nuclei in a given sample to undergo decay
Common Radioactive Isotopes
Isotope Half-Life Radiation Emitted
Carbon-14 5,730 years
Radon-222 3.8 days
Uranium-235 7.0 x 108 years
Uranium-238 4.46 x 109 years
Radioactive Half-Life
• After one half life there is 1/2 of original sample left.
• After two half-lives, there will be
1/2 of the 1/2 = 1/4 the original sample.• After three half-lives, there will be 1/2 of the 1/4
(or 1/8) the original sample• ….And so on….
Graph of Amount of Remaining Nuclei vs Time
A=Aoe-t
A
Half-Life Related Calculations• How to calculate number of half-lives (1/2 x 1/2x…)• How to calculate how old something is (no. of half-
lives x time per half-life)• Calculate amount remaining (A) after a certain
number of half-lives
A = Ao (where Ao = original amount)
2n (where n = no. of half-lives)• Calculate percentage remaining
__1_x 100%
2n (where n = no. of half-lives)
Example
You have 100 g of radioactive C-14. The half-life of C-14 is 5,730 years.
• How many grams are left after one half-life? Answer: 100 g
50 g
• How many grams are left after two half-lives?
Problem
A sample of 3x107 Radon atoms are trapped
in a basement that is sealed. The half-life of
Radon is 3.83 days. How many radon atoms
are left after 31 days?
answer:1.2x105 atoms
Group and Independent Practice
• Determining Half-Lives Practice Set
– Practice 2 of problems as a group
Part IV
Fission and Fusion
From Bill Nye the Science Guy
• Nuclear Power – link to Discovery Education website
FISSION
Nuclear FissionNuclear Fission
Nuclear FissionNuclear FissionFission is the splitting of atomsFission is the splitting of atoms
These are usually very large, so that they are not as These are usually very large, so that they are not as
stablestable
Fission chain has three general steps:Fission chain has three general steps:
1.1. Initiation.Initiation. Reaction of a single atom starts the Reaction of a single atom starts the
chain (e.g., chain (e.g., 235235U + neutron)U + neutron)
2.2. PropagationPropagation. . 236236U fission releases neutrons that U fission releases neutrons that
initiate other fissionsinitiate other fissions
3. 3. Produces enormous amounts of energyProduces enormous amounts of energy
Nuclear Fission & Nuclear Fission & POWERPOWER
• Currently about 103 Currently about 103
nuclear power plants in nuclear power plants in
the U.S. and about 435 the U.S. and about 435
worldwide.worldwide.
• 17% of the world’s 17% of the world’s
energy comes from energy comes from
nuclear.nuclear.
Figure 19.6: Diagram of a nuclear power plant.
Fission
• Benefits– A lot of energy can be
produced from a small amount of raw material
• 1 ton of nuclear material = 1 million tons of coal or 1 million barrels of oil
– Clean source of energy generation – not air polluting like fossil fuels
– Long term source of fuel
• Concerns– Safety accidents have
potential for horrendous harm (immediate and long term, such as cancer)
– No good way to dispose of high level nuclear waste
– Expensive construction and maintenance costs
FUSION
Nuclear Fusion
Fusion
small nuclei combine
2H + 3H 4He + 1n +
1 1 2 0
Occurs in the sun and other stars
Energy
Nuclear Fusion
Fusion
• Excessive heat can not be contained
• Attempts at “cold” fusion have FAILED.
• “Hot” fusion is difficult to contain
Fusion
• Benefits– A lot of energy can be
produced from a small amount of raw material
• 1 ton of nuclear material = 1 million tons of coal or 1 million barrels of oil
– Clean source of energy generation – not air polluting like fossil fuels
– Long term source of fuel– Doesn’t create hazardous
radioactive wastes as does nuclear fission
• Concerns– Occur at extremely high
temperatures – like that of sun
– Cannot sustain the reactions long enough to be useful for power generation
– Safety accidents have potential for horrendous harm (immediate and long term, such as cancer)
– Expensive construction and maintenance costs
Part V
Uses of Nuclear Chemistry
Radiocarbon DatingRadiocarbon DatingRadioactive C-14 is formed in the upper atmosphere Radioactive C-14 is formed in the upper atmosphere
by nuclear reactions initiated by neutrons in by nuclear reactions initiated by neutrons in cosmic radiationcosmic radiation
1414N + N + 11oon ---> n ---> 1414C + C + 11HH
The C-14 is oxidized to COThe C-14 is oxidized to CO22, which circulates through , which circulates through
the biosphere.the biosphere.
When a plant dies, the C-14 is not replenished.When a plant dies, the C-14 is not replenished.
But the C-14 continues to decay with tBut the C-14 continues to decay with t1/21/2 = 5,730 years. = 5,730 years.
Activity of a sample can be used to date the sample.Activity of a sample can be used to date the sample.
Nuclear Medicine: Nuclear Medicine: ImagingImaging
Thyroid imaging using Tc-99mThyroid imaging using Tc-99m
Food Food IrradiationIrradiation
•Food can be irradiated with Food can be irradiated with rays from rays from 6060Co Co
or or 137137Cs.Cs.•Irradiated milk has a shelf life of 3 mo. Irradiated milk has a shelf life of 3 mo.
without refrigeration.without refrigeration.•USDA has approved irradiation of meats and USDA has approved irradiation of meats and
eggs.eggs.
Part VI
Hazards of Radiation
Effects of RadiationEffects of Radiation
Summary
• Nuclear Radiation can be naturally occurring or man-made
• Most of radiation we are exposed to is naturally occurring – alpha rays
• Alpha Radiation – weakest (blocked by paper or cloth)• Beta Radiation – medium (blocked by wood or foil)• Gamma Radiation – strongest (blocked by lead or
concrete)
• Key Nuclear Science Pioneers – Henri Beckerel, Marie
and Pierre Curie
Summary
• How to Write Nuclear Notation - see blue graphic organizer
• Symbols for:Beta Particles Alpha Particles
Positrons Neutrons
Gamma Rays γ
Atomic Mass
Atomic No. Element symbol
1n0
Summary• Balancing Nuclear Equations (Law of Conservation of
Mass)
• Add coefficients in front of nuclear particles
SUMMARY - Half-Life Calculations• How to calculate number of half-lives (1/2 x ½ x…) or
1/amount remaining (as decimal or fraction) = 2n where n = no. half-lives
remember percent remaining = 100 – percent decayed
• How to calculate how old something is (no. of half-lives x time per half-life)
• Calculate amount remaining (A) after a certain number of half-lives
A = Ao (where Ao = original amount)
2n (where n = no. of half-lives)• Calculate percentage remaining
__1_x 100%
2n (where n = no. of half-lives)
Summary– Describe the difference between:– fission (splitting atoms)
• 3 steps – Initiation– Propagation– Production of large amounts of energy
– fusion (combining nuclei)– Describe the pros and cons of each– Describe examples of fission and fusion
– Examples of beneficial and harmful radiation sources• Power generation• Medical imaging, diagnostics, disease treatments• Food safety• Other – historical dating, smoke detectors, etc.
– Know what percentage of US and world energy comes from nuclear material. Know the country that leads in nuclear usage.
Extra
• Discovery Learning Video – Chemistry Connections: Nuclear Changes
• Radioactivity Homework