Nuclear Chemistry Last revision: M. Jones Pisgah High School

Atomic Theory

Atomic Theory Atoms are the smallest particles of elements. Atoms were first proposed by Democritus over 2000 years ago. The idea of atoms was reintroduced in 1803 by John Dalton.

1.Atoms are tiny, discrete particles 2.Atoms are indestructible 3.Atoms of the same element have the same mass and properties 4.Atoms combine in simple whole- number ratios 5.Atoms in different ratios produce different compounds. Dalton’s Atomic Theory

1.Atoms are tiny, discrete particles 2.Atoms are indestructible 3.Atoms of the same element have the same mass and properties 4.Atoms combine in simple whole- number ratios 5.Atoms in different ratios produce different compounds. We know that parts of Dalton’s atomic theory are no longer valid in today’s modern Quantum Mechanical model of the atom. Dalton’s Atomic Theory

1.Atoms are tiny, discrete particles 2.Atoms are indestructible 3.Atoms of the same element have the same mass and properties We know that atoms are made up of smaller particles, and that there are slight differences between atoms of the same element - isotopes. Dalton’s Atomic Theory

Atomic Theory We know that atoms are made up of protons, neutrons and electrons. Protons and neutrons are located in a small, dense, positively charged nucleus. We know that atoms are mostly empty space.

Atomic Theory In 1897 J. J. Thomson discovered that cathode rays were actually streams of subatomic particles. These particles carried a negative charge and were called electrons.

Cathode ray tube

Atomic Theory We know atoms are mostly empty space and that protons and neutrons are located in a small, dense, positively charged nucleus because of Rutherford’s explanation of the alpha scattering (gold foil) experiment.

+ Most of the alpha particles pass through undeflected. Atomic Theory  source

+ Some positive alpha particles are repelled by the small, dense, positively charged nucleus. Atomic Theory  source

Atomic Theory We know that electrons are outside the nucleus in an “electron cloud”. Electrons exist in specific energy levels, which explains the line spectra of the elements. Started with the Bohr model.

Atomic Theory We now use the Quantum Mechanical Model of the atom. Quantum Theory describes the nature of electrons and their interactions with the electrons of other atoms in chemical reactions.

Atomic Theory The subatomic particles that make up atoms have known properties like mass and electrical charge. Our understanding came through the efforts of a number of scientists like Thomson, Millikan, Rutherford, and Chadwick.

PropertyProtonNeutronElectron Symbols Location Rel. mass Mass (amu) Mass (g) Rel. charge Charge (C) Fill in the chart with the correct information.

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location Rel. mass Mass (amu) Mass (g) Rel. charge Charge (C)

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location nucleus cloud outside nucleus Rel. mass Mass (amu) Mass (g) Rel. charge Charge (C)

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location nucleus cloud outside nucleus Rel. mass11 1 / 1837 Mass (amu) Mass (g) Rel. charge Charge (C)

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location nucleus cloud outside nucleus Rel. mass11 1 / 1837 Mass (amu) amu amu amu Mass (g) Rel. charge Charge (C)

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location nucleus cloud outside nucleus Rel. mass11 1 / 1837 Mass (amu) amu amu amu Mass (g) 1.673x x x Rel. charge Charge (C)

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location nucleus cloud outside nucleus Rel. mass11 1 / 1837 Mass (amu) amu amu amu Mass (g) 1.673x x x Rel. charge+10 Charge (C)

PropertyProtonNeutronElectron Symbols p + and 1 H 1 n 0 and 0 n 1 e - and -1 e 0 Location nucleus cloud outside nucleus Rel. mass11 1 / 1837 Mass (amu) amu amu amu Mass (g) 1.673x x x Rel. charge+10 Charge (C) +1.6x C x C

Subatomic particles - Summary 1.Protons and neutrons are located in the nucleus. 2.Protons and neutrons have almost the same mass. Neutrons heavier. 3.Electrons are outside the nucleus and much lighter than proton or neutron. 4.Protons and electrons have the same charge but opposite polarity. 5.Neutrons have no charge.

Isotopes

Isotopes … Therefore, isotopes of the same element have different masses. …of the same element have the same number of protons and electrons but different numbers of neutrons.

Isotopes … …don’t have to be radioactive. Some isotopes are unstable and decay, releasing alpha or beta particles, or gamma rays. But, there are many stable isotopes that don’t decay.

Isotopes … Mass number - the sum of the protons and neutrons in the nucleus. Atomic number - the number of protons in the nucleus of an atom. …have different mass numbers but the same atomic number.

Symbols for Isotopes E A Z Symbol of Element Mass number Atomic number A is the symbol for mass number Z is the symbol for atomic number

U Symbols for Isotopes Symbol of Element Mass number Atomic number An isotope of uranium

Symbols for Isotopes U Mass number Symbol of Element Atomic number An isotope of uranium This form solves the word processor dilemma.

U -235 Symbol of Element Mass number How do you know the atomic number? Find U in the periodic table. Symbols for Isotopes Z = 92

Some elements have several Isotopes Lead has four naturally occurring isotopes, Pb-204, Pb-206, Pb-207, and Pb-208; but there are 23 man- made isotopes of lead.

Some elements have several Isotopes Bismuth has only one naturally occurring isotope, Bi-209, but there are 22 man-made isotopes of bismuth.

Finding the number of Protons, Neutrons, and Electrons The number of electrons in a neutral atom equals the number of protons. The atomic number is the number of protons in the nucleus.

neutrons = A - Z The number of neutrons is the difference between the mass number and the atomic number. Finding the number of Protons, Neutrons, and Electrons

Look at the periodic table and find the element by using the symbol. U-235 A = 235 protons + neutrons = 235 Z = 92 protons = 92 electrons = 92 Finding the number of Protons, Neutrons, and Electrons

U-235 A = 235 protons + neutrons = 235 Z = 92 protons = 92 electrons = 92 Finding the number of Protons, Neutrons, and Electrons How many neutrons are in a U-235 atom?

U – 92 = 143 neutrons Z = 92 protons = 92 electrons = 92 Finding the number of Protons, Neutrons, and Electrons How many neutrons are in a U-235 atom?

Q. Find the number of neutrons in the Ba-137 isotope. A. In the Ba-137 isotope … … Z = 56 and A = – 56 = 81 neutrons Finding the number of Protons, Neutrons, and Electrons

Copy the following table on notebook paper, and fill in the blanks. Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e Zinc66 In Rn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e Zinc66 In Rn Stop! Complete the table, then go on. Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e Zinc66 In Rn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e ZincZn In Rn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e ZincZn IndiumIn Rn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e ZincZn IndiumIn StrontiumSr Rn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e ZincZn IndiumIn StrontiumSr LeadPb Rn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e ZincZn IndiumIn StrontiumSr LeadPb RadonRn Finding the number of Protons, Neutrons, and Electrons

ElementSymbolZA#p#n#e ZincZn IndiumIn StrontiumSr LeadPb RadonRn BromineBr Finding the number of Protons, Neutrons, and Electrons

Atomic mass is the weighted average of all the isotopes of an element Boron has two isotopes: B %10.01 amu B %11.01 amu x x = amu

Atomic mass is the weighted average of all the isotopes of an element Determine the atomic mass of silicon: Si % amu Si % amu Si % amu x x x = amu

Consider the two isotopes of chlorine. Which isotope is more abundant? Cl - 35??.?? %34.97 amu Cl - 37??.?? %36.97 amu The average atomic mass is amu. Atomic mass is the weighted average of all the isotopes of an element

Consider the two isotopes of chlorine. Which isotope is more abundant? Cl %34.97 amu Cl %36.97 amu The average atomic mass is amu. Atomic mass is the weighted average of all the isotopes of an element

Which isotope of neon is more abundant? Ne-20 or Ne-22 Atomic mass is the weighted average of all the isotopes of an element Ne-2090% Ne-2210%

How are isotopes of the same element alike and different? Alike: 1.Number of protons and electrons 2.Atomic number 3.Chemical properties Different: 1. Number of neutrons 2. Mass Number 3. Atomic mass of the isotopes

Which of the following is the same for the three isotopes of magnesium? 1.The atomic number of 12 2.The number of protons and electrons 3.The number of neutrons 4.The atomic weight of AMU 5.The reaction with hydrochloric acid 6.The speed of gaseous Mg atoms

1.The atomic number of 12 All three isotopes of magnesium have the same atomic number. Same Which of the following is the same for the three isotopes of magnesium?

2. The number of protons and electrons All isotopes of the same element have the same number of protons in the nucleus, and electrons outside the nucleus. Same Which of the following is the same for the three isotopes of magnesium?

3. The number of neutrons The number of neutrons varies with the isotope. Different isotopes have different numbers of neutrons. Not the same Which of the following is the same for the three isotopes of magnesium?

4. Atomic weight of AMU Mg-24  AMU Mg-25  AMU Mg-26  AMU Not the same Which of the following is the same for the three isotopes of magnesium?

5. The reaction with HCl All isotopes of the same element react the same chemically. Same The number and arrangement of electrons is the same for each isotope. Which of the following is the same for the three isotopes of magnesium?

6. The speed of gaseous Mg atoms The speeds of atoms depend on mass. Heavier atoms move more slowly, and lighter atoms move faster. Not the same Which of the following is the same for the three isotopes of magnesium?

How did knowing about Graham’s Law allow the United States to win World War II?

Who were the two guys responsible for winning World War II? Fat Man, and …Little Boy Atomic bombs dropped on Hiroshima and Nagasaki

Hiroshima

Nagasaki

Manhattan Project Oak Ridge, TN Gaseous diffusion Graham’s law Enriched uranium

Manhattan Project

Less than 1% of naturally occurring uranium is U-235 Manhattan Project Naturally occurring uranium is mostly U-238

To sustain a nuclear chain reaction, uranium must be at least 4% U-235. Manhattan Project Bomb grade uranium is over 90% U-235

The process of increasing the percentage of U-235 is called enrichment. The uranium for a nuclear reactor is around 4% U-235. Manhattan Project

Uranium ore is reacted with fluorine to make gaseous UF 6. Then the gaseous UF 6 is introduced into chambers with porous disks in the ends. Manhattan Project

The lighter UF 6 molecules containing U-235 effuse through the holes in the disk faster. There is more U-235 on the other side of disk. Manhattan Project

As the UF 6 continues to move through many, many disks, the percentage of U-235 atoms in the gas increases, resulting in enrichment. Manhattan Project

Graham’s Law says that gas molecules which weigh less, will move faster than molecules which weigh more. Manhattan Project

The enriched UF 6 containing a much higher percentage of U-235 atoms, is reacted with water to make uranium oxide and HF. The uranium oxide is dried and made into fuel pellets. Manhattan Project

Uranium Pellet Fuel rod assembly

Only one element has unique names for its isotopes … 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)

Demonstrations with radioactivity Recall what you have discovered about nuclear radiation.

Mica window (fragile) Wire (+ side of circuit) Metal shield (- side) Low pressure Ar gas Counter 2435 Geiger-Mueller Tube

GM Tube Rays leave the source Some hit the GM tube Most do nothing One ray may cause a discharge… Source and the detector clicks

GM Tube Filled with low pressure argon gas About 1% efficiency About 1 in 100 rays causes an electric spark between the case and the wire Each spark registers as a count or click on the counter

Properties of alpha, beta and gamma radiation

Subatomic particles H 1 1 e 0 n 1 0 proton neutron electron What do the numbers represent?

Mass number /Atomic number U 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 2 He 4. What is the atomic number of an  particle? 2 He 4

Alpha (  ) particles are the nuclei of helium atoms and have the symbol 2 He 4. 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 -1 e 0. What is the mass number of a  particle? -1 e 0

Beta (  ) particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1 e 0. No protons or neutrons in an electron. -1 e 0

Beta (  ) particles are high speed electrons ejected from the nuclei of atoms and have the symbol -1 e 0. None What 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 -1 e 0. Location 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.

Gamma rays have short wavelengths … and high energies. Increasing energy

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

Radioactive Source  Paper Aluminum foil Lead Alpha, Beta, Gamma

Radioactive Source   Paper Aluminum foil Lead Alpha, Beta, Gamma

Radioactive Source    Paper Aluminum foil Lead Alpha, Beta, Gamma

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 Table Property AlphaBetaGamma 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 Table Property AlphaBetaGamma Greek Letter Symbol Actually is… Atomic number Mass number Relative mass Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol Actually is… Atomic number Mass number Relative mass Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… Atomic number Mass number Relative mass Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number Mass number Relative mass Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number 2NA Mass number Relative mass Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number 2NA Mass number 40NA Relative mass Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number 2NA Mass number 40NA Relative mass 4 1 / 1837 NA Relative charge Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number 2NA Mass number 40NA Relative mass 4 1 / 1837 NA Relative charge +2NA Penetrating Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number 2NA Mass number 40NA Relative mass 4 1 / 1837 NA Relative charge +2NA Penetrating LowMediumHigh Shielding

Nuclear Properties Table Property AlphaBetaGamma Greek Letter  Symbol 2 He 4 -1 e 0 NA Actually is… He nucleuselectronEM energy Atomic number 2NA Mass number 40NA Relative mass 4 1 / 1837 NA Relative charge +2NA Penetrating LowMediumHigh Shielding 2.5 cm of air; anything else Metal, plastic or wood Lead or concrete

Protection from radiation 1.Shielding2. Distance How do you protect yourself from … Alpha Beta Gamma 2.5 cm of air, paper, skin aluminum, lead, other metals, wood, plastic, etc. up to a foot or two of lead, many feet of concrete

There are some kinds of radiation you can not protect your self from.

Gamma rays and high energy cosmic particles from space. But there is one kind of radiation hazard that you can protect against. Radiation

That hazard comes from the uranium beneath your feet. Uranium in the ground decays according to …

Uranium-238 decays through many steps to make stable lead-206 The uranium decay series

The uranium decay series Radon is the only gas in the series.

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.

Half life

What is half life? Half life is the time needed for one half of a radioisotope to decay. Suppose you start with 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 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 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 project 1.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 project 5.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 project mass time t 1/2

Half life project mass time 2.5 t 1/2 10 5

Half life project Activity (counts/min) Time (min) t 1/2 Exponential decay A = A 0 e -kt

Half life project Time (min) t 1/2 Activity (counts/min) background Radiation is “not a problem” when it falls below background level. 200

Half life project Questions: 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 project Questions: 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

Decay equations

Alpha decay In alpha decay, an alpha particle ( 2 He 4 ) is released from the nucleus. The alpha particle carries away two protons and two neutrons.

Alpha decay 92 U 238  2 He Th 234 alpha particle decay product

Alpha decay 92 U 238  2 He Th 234 The atomic number decreases by 2. The mass number decreases by 4.

Alpha decay These must add up to 238 These must add up to U 238  2 He Th 234

Alpha decay 86 Rn 220  2 He 4 + ??? Radon-220 decays by alpha emission. What is the decay product? 84 Po 216

Alpha decay Write the alpha decay equations for: Am 241  Po 216  Ra 226  2 He Np He Pb He Rn 222

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 decay Scientists 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 0 n 1  1 H e 0 neutronprotonelectron The electron ejected from the nucleus is a beta particle. Decay of a neutron:

Beta decay 0 n 1  1 H e neutronprotonelectron Technically, the decay of a neutron also involves a neutrino. anti- neutrino

Beta decay 0 n 1  1 H e neutronprotonelectron Actually, an anti-neutrino. anti- neutrino The word “neutrino” comes from Enrico Fermi, meaning “little neutral one” in Italian.

Beta decay 0 n 1  1 H e neutronprotonelectron A neutrino is a particle with no charge and almost no mass. anti- neutrino

Beta decay 0 n 1  1 H e neutronprotonelectron A neutrino carries off some of the energy in the decay of the neutron. anti- neutrino

Beta decay 0 n 1  1 H e neutronprotonelectron When predicting the products of beta decay we will ignore neutrinos. anti- neutrino

Beta decay Start 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 6 C 14  7 N e 0 beta particle decay product

Beta decay 6 C 14  7 N e 0 The atomic number increases by 1. The mass number stays the same.

Beta decay 6 C 14  7 N e 0 Notice that these add up to 6 These add up to 14

Beta decay Zn-69 decays by beta emission. What is the decay product? 30 Zn 69  -1 e 0 + ??? 31 Ga 69

Beta decay Write the beta decay equations for: Pb 214  Co 62  -1 e Bi e Ni ???  -1 e Cd Ag 113

Review: decay equations Alpha: Go down two on periodic table Atomic number decreases by 2 Mass number decreases by 4 Beta: Go up one on periodic table Atomic number increases by 1 Mass 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

Nuclear energy Forms of ionizing radiation are: Alpha Beta Gamma X-rays Cosmic rays Ultraviolet light (UV) can cause cancer, but it is not ionizing radiation. Neutrons Positrons

There’s even more! But there is an even greater release of energy when the atom splits apart … Some of the energy that holds the nucleus together is carried away by the alpha, beta and gamma radiation.

Nuclear Fission

Nuclear fission Fission – the splitting of an atom after being struck by a neutron.

Nuclear fission The neutrons strike other atoms causing more fission. Plus, two or three neutrons are released along with a great deal of energy. The atom splits into two or more fission fragments.

U-235 Nuclear fission Neutron Neutrons Fission fragment

Nuclear fission U-235 Neutrons Fission fragment These U-235 atoms can split when hit by neutrons, and release more neutrons, starting a chain reaction.

Nuclear fission To picture a chain reaction, imagine 50 mousetraps in a wire cage. And on each mousetrap are two ping-pong balls. Now imagine dropping one more ping-pong ball into the cage …

Detail of ping-pong balls on mousetraps.

Nuclear fission Billions of splitting atoms releases a huge amount of heat energy. This energy originally held the nucleus together. As the chain reaction proceeds, energy is released as heat energy.

Nuclear fission This heat energy can be harnessed to boil water, creating steam, that can spin a turbine, that can turn a generator, creating electricity.

Nuclear reactor

Reactor core Containment building Fuel rods Heat exchanger Steam generator Water circulates in the core Steam to turbine Water from cooling lake

Nuclear reactor Reactor core Containment building Fuel rods Water circulates in the core Steam to turbine Cadmium control rods – absorb neutrons

Water from cooling lake Nuclear reactor Reactor core Fuel rods Water circulates in the core Steam to turbine The water in the core serves two functions. (1) The water cools the core and carries away heat. (2) Water is a moderator. The water slows the neutrons so that they can cause fission. Fast neutrons do not cause fission. Containment building

Nuclear reactor Reactor core Containment building Fuel rods Water circulates in the core Water from cooling lake

Nuclear reactor Reactor core Containment building Fuel rods Water circulates in the core Water from cooling lake Heat exchanger Steam generator

Nuclear reactor Reactor core Containment building Fuel rods Water circulates in the core Water from cooling lake Heat exchanger Steam generator

Nuclear reactor Reactor core Containment building Fuel rods Water circulates in the core Water from cooling lake Steam to turbine Heat exchanger Steam generator

From nuclear energy to… Steam to turbine Water from cooling lake Cooling towers or lake turbinegenerator Transmission wires Condensed steam Heat exchanger Steam generator

Steam to turbine Water from cooling lake Cooling towers or lake turbinegenerator Transmission wires Condensed steam Heat exchanger Steam generator Electrical energy

Steam to turbine Water from cooling lake Cooling towers or lake turbinegenerator Transmission wires Condensed steam Heat exchanger Steam generator Electrical energy This part of the system is the same regardless of how the steam is produced. The heat can come from nuclear energy or by burning coal, natural gas or fuel oil.

Electrical energy In fact, the only purpose of a nuclear reactor is to boil water.

Pros and cons Cheap, plentiful power, no CO 2, nuclear waste, terrorist attack, running out of oil and coal, on- site storage, breeder reactors, transportation of spent fuel, “not in my backyard”, …

What about fusion?

Nuclear fusion is like a day without fusion. A day without sunshine

Nuclear fusion Is nuclear fusion an alternative to fission for producing electricity? Fusion occurs when hydrogen atoms combine to make helium, and release energy. Nuclear fusion powers the sun.

Nuclear fusion Now consumes more energy than it releases. Magnetic bottle. Control problems. Occurs at very high temperatures which nothing can withstand. Fusion not now technically feasible.

Nuclear Chemistry Developed by Mike Jones Pisgah High School Canton, NC