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

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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