chapter 25 nuclear chemistry chemical reactions- a rearrangement of atoms and molecules by breaking...
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Chapter 25Nuclear Chemistry
Chemical Reactions-A rearrangement of atoms
and molecules by breaking and forming bonds
-involves electrons
Nuclear Reactions-Combining, splitting or decay
the nuclei of atoms.
Chemical vs. Nuclear Reactions
Nuclear Chemistry involves the NUCLEUS of the atom.
That means…. the protons and neutrons will undergo a change (nuclear reactions)
Nuclear reactions usually involve radioactive elements
Radioactive Elements are NOT stable….
…because of the proton to neutron ratio.
Radioactivity & Radiation - Alpha, Beta, Gamma - YouTube
Radioactive elements will give off particles and energy until they
become stable (non-radioactive)
Radioactive elements change by themselves
Of the 119+ different atoms….
…there are more than 1500 different nuclei, only 264 are stable
Discovery of Radioactivity
Professor Roentgen – 1895- found that certain elements gave off X-rays but didn’t know what caused them.
•1896
•exposed a uranium-bearing
crystal to sunlight
•then placed it on a
photographic plate
the crystal produced an image
Antoine Henri Bacquerel
Bacquerel theorized…
…..that the absorbed energy of the sun was being released by the uranium in the form of x-rays
This theory was proven incorrect because when he didn’t expose it to light, he still got the image
Since the crystal produced its own image on the plate without being expose to sunlight, he theorized that the crystal produced its own rays.
HowStuffWorks Videos "100 Greatest Discoveries: Radioactivity"
-Marie Curie (1867-1943) and Pierre Curie (1859-1906)
Marie and Pierre Curie
-They found that uranium gave off particles from the nucleus- (shown by a change in mass)
-Won Nobel Prize in 1903 for this research
• Studied pure uranium vs. ore containing uranium
• ore was more radioactive than the pure material.
• Conclusion: ore contained additional radioactive components besides the uranium.
• This observation led to the discovery of two new radioactive elements, polonium and radium.
Next they……
-Marie won 2nd Nobel Prize in 1911 for finding the radioactive elements polonium and radium.
•1910 In honor of Marie and Pierre Curie……the Radiology Congress chose the curie as the basic unit of radioactivity
-Marie organized first mobile x-ray machines to be used in World War I
-Marie pioneered use of radiation in cancer treatment
-Marie died of leukemia in 1943.
Ernest Rutherford (1871-1937)
• father of nuclear physics. • Particles named and characterized by him include the alpha particle, beta particle and proton.
Nuclear Science• Began with Albert Einstein• E = mc2
• Energy= mass x (speed of light)2 • Speed of light - 299,792,458 m/s (meters
per second) or 186,000miles/second or 671 million miles/hr. (around earth in 1.3 seconds)
• very small amounts of mass may be converted into a very large amount of energy
The Case of the Doomed Dial
Painters
• In 1917, pretty Florence Kohler Casler was happily engaged in her first job. At the U.S. Radium Corporation’s plant in Orange, NJ, she sat by a table covered with watch dials. Tipping a tiny brush continuously with her tongue, she coated their numerals with luminous paint containing tiny amounts of radium. Two years later she quit and got married. In 1949, cancer developed in her sinuses. Last week, Florence Casler died, the 41st victim of the famous radium poisoning of the 1920’s.
• LIFE Magazine, December, 1951.
Radium watch dial painters
• In 1917, many young women working for the United States Radium Corporation thought they had found the perfect job. Wages were good and the work was easy. As watch dial painters, all they had to do was mix up a batch of glow-in–the-dark radium based paint and brush the paint on the watch dials. In order to apply the paint precisely, they were encouraged to “sharpen” the points of the brushes with their tongues.
At the time, radium- based glow-in-the-dark paint was a popular gimmick. People loved watches they could read in the dark. Some of the workers even painted their nails with it or sprinkled it in their hair. No one ever told them it was deadly.
In the early 1920s, however the dial painters started getting sick. The women began losing their teeth and suffering from gum ulcers, anemia, tumors and “jaw rot” – a painful decay of bone and tissue in the mouth. By 1924, 50 women were ill and a dozen had died.
Doctors and dentists were mystified. An increasing number of seemingly healthy young women were developing terrible symptoms and the only thing the women had in common was the fact that they had all worked at the same job for the United States Radium Corporation.
NOT US !Authorities at the New Jersey
Department of Labor failed to identify anything hazardous at the work site. The United States Radium Corporation accepted no responsibility, claiming that the women’s ills were due to “poor dental habits” or in the words of the company’s president, “a hysterical condition brought about by coincidence”. But some people suspected that radium was the cause.1
THE PLOT THICKENS
In 1925, Dr. Harrison S. Martland, the Medical Examiner of Essex County, was asked to investigate the death of a 36 year old man, who was employed as a chemist by the United States Radium Corporation. The man, who had been diagnosed with anemia, presented Dr. Martland with a puzzling situation. For a case of normal anemia, death had come much too quickly.2
Dr. Martland was intrigued. He consulted with an expert on radiation, Dr. Sabin A. Von Sochocky, a founder of the United States Radium Corporation and the inventor of the radium paint the workers had been using. Together, they analyzed tissue and bone from the chemist who had died. The results were startling. The chemist’s body was saturated with radioactivity! Dr. Martland and Dr. Von Sochocky suspected that others who had worked at the factory were contaminated, too.3
SOLVING THE MYSTERY
Dr. Martland and his team built a radiation detector (somewhat like a Geiger counter) and tested one of the dying dial painters. When she breathed into their detector, they saw that she was filled with radioactivity.
After the dial painter died, Dr.Martland removed a splinter of bone from her body. When he strapped a paper clip, a broken blade and dental x-ray film to the dead woman’s leg, her bone had absorbed so much radium that it emitted enough radiation to expose the film and silhouette the bits of metal.
Dr. Martland tested other painters. Whether they appeared healthy or sick, they were all radioactive. Von Sochocky tested himself and discovered that his breath contained higher levels of radioactivity than anyone else tested. He subsequently died “a horrible death”.4
(Aplastic anemia)
On December 5, 1925, Dr. Martland presented his finding in The Journal of the American Medical Association. For the first time, the deadly effects of radiation had been clearly established.5
• 1 Marc Mappen.”Jerseyana”. The New York Times, March 10, 1991, Sunday Late edition, Section12NJ,p.13
• 2 Ibid• 3Ibid• 4Ibid• 5Ibid
Substances that give off particles from the nucleus
are radioactive.
• Radioactivity -the process in which an unstable atom emits charged particles and energy to become a stable atom
• proton to neutron ratio determines what type of radiation is given off
Only certain isotopes (nuclides) are radioactive
• Nuclide- a specific nucleus• Nuclides that are radioactive are
called radioisotopes
Radioisotopes (unstable atoms)
-atoms with more than 83 protons are usually unstable
Transuranium Elements
•The elements past uranium (#92)
•All radioactive
Showing Radioactive Atoms.
Use Isotope Notation
C-12 C-14
CC12
Mass number
14
6
Atomic number
6
To become stable, radioisotopes give off
radiation (Radioactive decay)
Unstable atom
radiation
•Alpha Particle: α
•Beta Particle: β
•Gamma Ray: γ
Types of Radiation
Alpha Decay-when an atom gives off an alpha particle
Alpha Particle = 2p and 2n
-atomic # goes down 2 and atomic mass goes down 4
Alpha Decay
(in decay series)
or
He (in nuclear equations)
-Written as:
Ex.
-U-238 turns into Th-234 when it gives off an alpha particle
23892
U23490 Th+
42 He
(nuclear equation)
-weakest radiation
-can burn flesh
-can be stopped by a piece of paper.
Alpha Particles
Affects of Alpha Particles on Body
• will not penetrate the outer layer of skin• dangerous if inhaled or swallowed.• Cells in lining of the lungs or internal
organs will be changed (mutated) or killed
• lung cancer cases among uranium miners from inhaled and ingested alpha sources is much higher than those of the public at large.
•Radon gas
•produced by the decay of radium-226
• emits alpha particles
• poses a hazard to lungs and airways when inhaled.
Radon
- Written as
or
0-1e
Beta DecayTwo types:
Written as β+
0+1e
Beta minus decay Beta plus decay
A. BETA MINUS DECAY:• Neutron decays into a proton, an
electron and an antineutrino• Mass number remains the same but
atomic # increases by 1
228 88 Ra
Beta minus decay
n p + e- + antineutrino-
B. BETA PLUS (positron) DECAY• A proton decays into a neutron,
a neutrino and a positron• Mass number remains the same• Atomic Number decreases by 1
230 91 Pa
Beta plus decay
p n + positron+ + neutrino
-neutron breaks apart
-proton breaks apart
-100x more penetrating than an alpha particle
-can be stopped by clothing or wood-travel at the speed of light
-usually accompanies other modes of radioactive decay
Beta Particles
Which type of beta is given off?
(it depends on the proton to neutron ratio)
Too many neutrons = beta minus decay
n p + e- + antineutrino-
Ex.
C146
Too few neutrons – Beta plus decay
-Positron has the mass of an electron but is positively charged
10 6
Proton neutron + neutrino and positron
C
-gives off a gamma ray (γ )
- a release of high energy electromagnetic radiation from nucleus
-it’s pure energy not a particle
-Atomic # and mass stay the same, just changes to an atom with less energy
- needs thick walls of concrete or lead to stop it.
Gamma Decay
Nuclear equations
• Show one transformation of a decay series
• Must be equal on both sides. !!!!!!!!!
23793
Np
Alpha decay equation
Beta minus decay equation
3215
P
Beta plus decay equation (positron decay)
158
O
•Add or subtract the atomic mass and adjust the atomic number.
Other Particles Released from Nucleus and /or absorbed particles
Write the equation showing the release of a neutron from a U- 238 nucleus.
Absorbed Particles
Ex. Write the nuclear equation for when U-238 is bombarded with and absorbs an alpha particle
Decay Series
- shows the progression of changes a radioactive element goes through
-uses symbols:
α = alpha particle
β = beta particle
γ = gamma radiation.
Penetrating Power
Alpha, Beta and Gamma Radiation
Half- Life- the time it takes for half of the sample of a radioactive element to decay.
-half-lives are different for each element.
-ex. Rh-106 half-life = 30 seconds
U-238 half-life = 4.5 billion years
Half Lives
• Radioisotope Half-life• Radon-222 4 days• Strontium-90 28 years• Radium-226 1602 years• Plutonium-239 24 400 years• Uranium-235 700 000 000
years
Half-life of a Radioactive Element?
What is the half-life of Cesium-137?
What is the half-life of Sodium-24?
How many half-lives does Na-24 undergo in 45 hours?
Half-Life ProblemCs-129 has a half-life of 32.0 hours. If you start with 130grams of Cs-129, how many grams will be remaining
after 12 days?
First determine # of half-lives it will go through
Then divide the amount in half(2) to the power of half-lives
Transmutation-when an element changes into a different element. (* hint: Proton # must change)
3 ways it can occur:
1. Radioactive decay
2. Bombard nucleus with a particles or neutrons3. Expose to extremely high temp. causing nuclei to fuse
Artificial
natural
Natural Background Radiation- where does it
come from?• Cosmic radiation – comes from the
sun
Terrestrial radiation – comes from radioactive elements found in earth’s crust.
Where do we get the most radiation exposure?
In addition to all the other chemicals in cigarettes, the tobacco leaves used in making cigarettes contain radioactive material, particularly lead-210 and polonium-210.
Need another reason why not to smoke?
Effects of Radiation
1. Damages or kills cells and tissues2. Alters DNA
3. Reddening of skin
4. Drop in white blood cell count
5. Nausea, fatigue, hair loss
6. Weakens metals
Instruments for Detecting Radiation
1. Geiger Counter
2. Cloud chamber
Cloud Chamber
• The thickness and length of the cloud trail is different for alpha and beta particles, so they are able to distinguish between them
3. Bubble chamber- they show actual trails of bubbles that are formed as charged particles force their way through an unstable liquid.
Uses of Radioactive materials
1. Production of electricity
States with Nuclear Warheads (shown in red)
2. Warheads and Atomic Bombs, and nuclear submarines
3. Radioactive dating – used to date artifacts
4. Tracers –a chemical compound in which one or more atoms have been replaced by a radioisotope
- Used in industries and medicine
- - Radioisotopes of hydrogen, carbon, phosphorus, sulfur, and iodine have been used extensively to trace the path of biochemical reactions.
- used to track the distribution of a substance within a natural system such as a cell or tissue.
Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production.
5. Radiation treatments are used to kill abnormal cells
6. Food irradiation
Radura
7. Mail irradiation – post 9/11- Anthrax scare
The Beginnings of the Nuclear Age 1934-1938
• After discovery of neutron, scientists began to “Play”
• Bombarded nuclei of Uranium atoms with neutrons
• Caused uranium nucleus to split
Two Kinds of Nuclear Reactions
1. Fission-
Splitting the nucleus
2. Fusion-
Combining nuclei
During a nuclear reaction small amounts of mass are changed into large amounts of energy
E = mc2
Nuclear Fission-Splits nucleus of atom
- releases a tremendous amt. of energy
-used in reactors and atomic bombs
-Dangerous because of radioactive wastes and possible leaks
• low speed neutron is captured by a uranium-235 atom
• Atom becomes unstable and splits into various products
• energy and high speed neutrons are released
Nuclear Fission: How it causes the atom to split
Neutron Moderation
• Normally, neutrons move too fast to be captured by the nucleus
• Slows down neutrons so reactor fuel can capture them and use them.
Chain Reaction
by Otto Hahn in 1939
1st Proven Nuclear Fission Experiment
-Enrico Fermi –1942- produced 1st nuclear chain reaction
-July 16, 1945 – 1st atomic bomb tested in New Mexico
1951-1st 4 electric bulbs lit by electricity produced by experimental breeder reactor in Idaho Falls
1953-1st two nuclear submarines Nautilus and Seawolf
1954-1st Nuclear Power plant in Soviet Union
-1956 –1st commercial nuclear power plant opened in England
-1956 – 1st commercial power plant in U.S. (Shippenport, PA)
Nuclear Power Plant
reactorCooling tower
Nuclear Power Plants
- U.S. power plants provide about 20% of our power.
-fission reactions (split atoms)
-monitored by the NRC Nuclear Regulatory Commission
How a Nuclear Power Plant Produces Electricity
Controlling a reactor
• Control rods in reactor absorb some of the slow moving neutrons so they can’t become part of the reaction.
• Prevents the reaction from going too fast
• In Chernobyl accident, too many control rods were removed and the reaction went critical
Cooling Tower
Nuclear Power Plant Control Room
Nuclear Waste
• Used fuel rods contain some remaining fuel and products that are radioactive
Used rods are stored in pools of boric acid to cool them down and act as shield to reduce radiation
levels.
Neutron absorbing material is also placed between the rods to prevent them from reacting
Dry Cask Storage Containers are used to help overcrowded temporary storage pools
Yucca Mountain, Nevada-planned off-site storage
facility to be built by government.
-has dry , relatively stable groundScheduled to be completed by 2010
The Massive TBM (Tunnel Building Machine) Used to Dig the Tunnels Into
Yucca Mountain
Eureka County, Nevada -- Yucca Mountain.org -- What's New
Yucca Mtn. Debate
• President Obama – closed Yucca Mtn.• In contrast to GOP leaders in Congress, Jon Huntsman,
Tim Pawlenty, Gary Johnson and Ron Paul have all come out in opposition to storing the nation’s nuclear waste at Yucca Mountain. Other Republican candidates, including Newt Gingrich, Rick Santorum and Michele Bachmann, have ripped the Obama administration’s effort to close Yucca. Mitt Romney, who won the 2008 Nevada GOP caucus, has not taken a firm stance on the controversial issue.
Salem
Oyster Creek
Hope Creek&
NJ Nuclear Power Plants
Hope Creek Power Plant, NJ
Harrisburg, PA
3 Mile Island Nuclear Power Plant
Buchanan, NY
Indian Point Power Plant
Nuclear Power Plants in U.S.
Chernobyl
-1977 – Reactor built in Chernobyl, Russia
http://www.youtube.com/watch?v=bSRC1_OZPIg
1986 - Worst nuclear reactor accident in history.
-April 26th – explosion throws tons of radioactive fuel into atmosphere-May 4- Soviet government releases info. about accident.
-May 5th – radiation reaches west coast of U.S.
-May 8th – reactor still burning
-May 25th – experts say it was human error
-June 24th – concrete slab under reactor completed
-Nov. 15th – concrete sarcophagus surrounding reactor completed
-May 7th – ban on food and animals exported from USSR, Poland, Romania, Bulgaria, Czech. And Yugoslavia
-1990 – 10 billion rubles given in foreign aid to repair
-sarcophagus is leaking earlier than expected.
-1996 Chernobyl Shelter Fund was established
-with help from U.S. and many other nations loans have been secured to rebuild sarcophagus (2005) and clean up area
The aftermath of Chernobyl
Chernobyl today. The middle of the picture shows concrete sarcophagus surrounding the fatal reactor number four.
http://teachertube.com/viewVideo.php?
video_id=218366&title=Children_of_Chernobyl
Fission vs. Fusion
1. Fission – used today
2. Fusion – promising for the future
Nuclear Fusion-the joining of two nuclei to form one.-produces a tremendous amt. of energy
• light elements combine to form heavier elements, giving off energy
• takes place in the stars • core of the sun, temperatures of 10-15
million degrees Celsius • hydrogen is converted to helium
Nuclear Fusion
-fuel is plentiful and less dangerous.
-waste is safe.
-must be over 1 million oC to start.-more difficult to control.
• isotopes of hydrogen• deuterium H-2 (D)• and tritium H-3 (T)• fuse to form helium and a
single neutron, giving off energy
Proposed Fusion Reactors
Fusion of Deuterium and Tritium
ITER• Experimental fusion reactor• A safe, non-polluting nuclear reaction• 30 year program – 10 year construction, 20
years of operation (beginning in 2016)• To be built in Cadarache, France• Hopes to produce 500MWof energy from
50MW by fusing deuterium and tritium• Will produce 3X more energy than a U-238
fission reaction• It hopes to be the power resource of the
future
Cold Fusion*still not proven it can work.
1. Start with deuterium, send in pulses of sound wave, then blast the fluid with neutrons
How they say it works.
2. Neutrons create bubbles which cause the sound waves to rapidly expand and contract3. Contractions release enough energy to fuse atoms
HST Modern Marvels - Inviting Disaster: Three Mile Island
(2003) - YouTube
HowStuffWorks Videos "Brink: Evidence of Nuclear Fusion?"
History of Nuclear Power and the US Navy Submarine (1967) -
YouTube
TeacherTube Videos - chernobyl