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Wilhelm Rontgen • 1895 German Scientist Playing with a Crookes tube
• Sitting in a dark lab, tube covered with black paper, held up a book to the tube . . .
• Image of key appeared on paper painted with Barium across the room
• The key had been a bookmark
Rontgen’sLab
• Rontgen thought he was hallucinating • Told no one• Shut himself in the dark lab for seven weeks• Held up a metal plug and saw … his BONES
“Black Magic”• Took a picture of wife’s
hand (afraid, she never went back to the lab)
• Showed that these images were real
• Rontgen began to document and rationalize his work w/ physics knowledge of the time
The Nobel Prize in Physics 1901
Wilhelm Conrad RöntgenNamesake Element:
Rontegenium• Atomic # 111• Atomic Weight 272
Discovered in 1994, Germany
Highly Radioactive, but this element does not emit x-rays
FUSION AND FISSION
First, a little bit about energy
Forms of Energy
• The five main forms of energy are:
– Heat
– Chemical
– Electromagnetic
– Nuclear
– Mechanical
Heat Energy
• The internal motion of the atoms is called heat energy, because moving particles produce heat.
• Heat energy can be produced by friction.
• Heat energy causes changes in temperature and phase of any form of matter.
Chemical Energy
• Making and Breaking bonds• Chemical Energy is required to bond
atoms together.• And when bonds are broken, energy is
released.
Chemical Energy
• Fuel and food are forms of stored chemical energy.
Electromagnetic Energy
• Power lines carry electromagnetic energy into your home in the form of electricity.
Electromagnetic Energy
• Light is a form of electromagnetic energy.
• Each color of light (Roy G Bv) represents a different amount of electromagnetic energy.
• Electromagnetic Energy is also carried by X-rays, radio waves, and laser light.
Mechanical
• Kinetic /Potential
Nuclear Energy
• The nucleus of an atom is the source of nuclear energy.
• Energy holding nucleus together
Nuclear Energy
• Nuclear Energy is the most concentrated form of energy!
• 2 major reactions :Fission & Fusion
Fusion• Nuclear fusion is the process by which
multiple nuclei join together to form a heavier nucleus.
• The fusion of two nuclei lighter than iron or nickel generally releases energy.
• The fusion of nuclei heavier than them absorbs energy.
Result: gain or loss of energy
Nuclear Fusion
Nuclear Fusion Example
The sun’s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei.
NUCLEAR FISSION
• Fission may be defined as the process Fission may be defined as the process of of splitting an atomic nucleus splitting an atomic nucleus into into fission fragmentsfission fragments
• The fission fragments are generally in The fission fragments are generally in the form of smaller atomic nuclei and the form of smaller atomic nuclei and neutronsneutrons
• Large amounts of energy are Large amounts of energy are produced produced by the fission processby the fission process
More about fission
• Fissile nuclei are generally Fissile nuclei are generally heavy atoms heavy atoms with large numbers of nucleonswith large numbers of nucleons
• The nuclei of such heavy atoms are The nuclei of such heavy atoms are struck by neutrons initiating the fission struck by neutrons initiating the fission processprocess
• Fission occurs due to electrostatic Fission occurs due to electrostatic repulsion created by large numbers of repulsion created by large numbers of protons within the nuclei of heavy atomsprotons within the nuclei of heavy atoms
Nuclear FissionNeutron induced in U235
Neutrons may:1 - Cause another fission by colliding with a U235 nucleus
2 - Be absorbed in other material
3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y
• Creates two smaller nuclides and free neutrons• The free neutrons potentially collide with nearby U235 nuclei• May cause the nuclide to split as well
Fission Example
Where does the energy come from?
We often say that matter cannot be created nor destroyed. However . . .
Einstein taught us that Energy and matter are different forms of the same thing!
E = mc2
04/21/23
Mass Defect
• The nucleus– is composed of protons and neutrons– the actual mass is less than the mass of
the separate particles.
• The "missing" mass is in the form of energy holding the nucleus together.
04/21/23
Uranium-238
238U92
A proton is 1.00728 amu A neutron is 1.00867 amu
What mass is expectedfor the nucleus of 238U?
atomic number(protons)
nucleons(protons & neutrons)
The nuclear massof uranium-238 is238.0003 amu
04/21/23
Uranium-238
(92)(1.00728) = 92.6698(146)(1.00867) = 147.2658
92 protons146 neutrons
predicted mass = 239.9356
actual mass = 238.0003
mass defect = 1.9353 amu
04/21/23
Masses of Atoms
The nuclear mass of 238U is 238.0003
Why does the Handbook of Chemistry and Physicslist the mass of uranium238 as 238.0508?
(92)(0.0005488) + 238.0003 = 238.0508
04/21/23
Binding Energy
• The mass defect indicates the total energy involved in holding the nucleus together.
• To determine the stability of the nucleus, the binding energy per nuclear particle is a better measure.
Binding Energy of 238U
predicted mass239.9356
actual mass238.0003
1.9353 amu
E = mc2 = 931.5 MeV/amu
What is the binding energy per nucleon of 238U?
04/21/23
Binding Energy of 238U
Binding energyper nucleon =
(1.9353 amu)(931.5 MeV/amu)238 nucleons
= 7.57 MeV
04/21/23
Binding Energy
The nuclei with the greatestbinding energy per nucleon
are the most stable.
62Ni
E = mc2
• Matter can be changed into energy • In the equation above:
– E = energy– m = mass– c = speed of light
• Small amount of mass becomes a HUGE amount of energy
Chemical Reactions
• Involve changes in electrons– Acids & Bases,
combustion, displacement• The same atoms appear
on both sides of the reaction.
• Follows Dalton’s Law of Conservation of Mass
• Small amount of energy generated– Burning fossil fuels
Nuclear Reactions
• Involve changes in the nucleus– Nuclear fusion, nuclear
fission• New atoms appear as
products of the reaction.
• Breaks Dalton’s Law of Conservation of Mass
• Large amount of energy generated – 1 million times more than
chemical reactions– Nuclear fusion on the sun– Nuclear fission for reactors
Decay vs. Nuclear Reactions• Alpha, beta, and gamma
decay occur as ONE atom tries to increase it’s stability by getting rid of a few neutrons, or protons & neutrons.
• The product is an alpha, beta, or gamma particle and ONE new atom. There is only ONE thing on the left hand side.
• Nuclear reactions involve more than just getting rid of a few protons or neutrons. The new atoms produced are VERY different elements than the reactant.
• Nuclear reactions must be started, so there are 2 things on the left hand side.– Nuclear fission: makes 2
or more much smaller atoms
– Nuclear fusion: makes 1 much larger atom
Nuclear Fission
What are the differences between the 2 above nuclear equations??
Alpha Decay
Review
• Mass and Energy are two forms of the same Mass and Energy are two forms of the same thing; neither can be created nor destroyed thing; neither can be created nor destroyed but mass can be converted into energy (E = but mass can be converted into energy (E = mcmc22))
• Fission is a nuclear reaction in which a heavy Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic atomic nucleus is split into lighter atomic nucleinuclei
• Fusion is a nuclear reaction in which 2 light Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, atomic nuclei are combined into a single, heavier atomic nucleusheavier atomic nucleus
Quiz
• Which nuclear process produces large Which nuclear process produces large amounts of energy?amounts of energy?
A. FissionA. Fission
B. FusionB. Fusion
C. Both fission & fusionC. Both fission & fusion
D. Neither fission nor fusionD. Neither fission nor fusion
Quiz
• Fission is the process that _________ Fission is the process that _________ atomic nuclei.atomic nuclei.
A. CombinesA. Combines
B. Burns upB. Burns up
C. StoresC. Stores
D. SplitsD. Splits
Quiz
• Mass may be converted into energy.Mass may be converted into energy.
A. TrueA. True
B. FalseB. False
Quiz
• The fission process requires heavy The fission process requires heavy atomic nuclei.atomic nuclei.
A. TrueA. True
B. FalseB. False
Quiz
• Name a nuclear reaction that occurs Name a nuclear reaction that occurs within the sun:within the sun:
Bonus
• Explain this equation:Explain this equation:
E = mcE = mc22