Chapter 22Chapter 22Nuclear ReactionsNuclear Reactions

Chemical ReactionsChemical Reactions

Occur in the outer electron energy levelOccur in the outer electron energy level Valance electronsValance electrons Ionic or covalent bonding occursIonic or covalent bonding occurs

Nuclear ReactionsNuclear Reactions

Occur in the nucleus of the atomOccur in the nucleus of the atom

Involve the Involve the NUCLEONSNUCLEONS

Nucleons = protons & neutronsNucleons = protons & neutrons

Transmutation occursTransmutation occurs

Strong Nuclear ForceStrong Nuclear Force

Protons are positively charged and repel Protons are positively charged and repel each other each other

←←+ ++ +→→ Strong Nuclear ForceStrong Nuclear Force = the force that = the force that

causes the protons and neutrons in the causes the protons and neutrons in the nucleus to stick together and holds the nucleus to stick together and holds the nucleus tightly together.nucleus tightly together.

ISOTOPESISOTOPES

Atoms of the same element Atoms of the same element with a different number of with a different number of neutrons.neutrons.

Ex: carbon-12 & carbon-14Ex: carbon-12 & carbon-14 Carbon-12Carbon-12

6 protons6 protons 6 neutrons6 neutrons 6 electrons6 electrons

Carbon-14Carbon-14 6 protons6 protons 8 neutrons8 neutrons 6 electrons6 electrons

3 Types of Radioactivity3 Types of RadioactivityRadioactive DecayRadioactive Decay

ALPHA PARTICLE ALPHA PARTICLE ((αα))

BETA PARTICLE BETA PARTICLE ((ββ))

GAMMA RAYS GAMMA RAYS ((γγ))

ALPHA ALPHA PARTICLEPARTICLE 2 protons & 2 neutrons2 protons & 2 neutrons nucleus of a helium atomnucleus of a helium atom weakest type of radiationweakest type of radiation can be stopped by a piece of papercan be stopped by a piece of paper 12 inches max. distance travel12 inches max. distance travel

What happens to the numbers What happens to the numbers of particles in the nucleus after of particles in the nucleus after alpha decay?alpha decay?

BETA BETA PARTICLEPARTICLE

an electron emitted from the nucleusan electron emitted from the nucleus A neutron splits into a proton & electronA neutron splits into a proton & electron The electron is expelled out of the nucleusThe electron is expelled out of the nucleus The proton stays and increases the number of protons The proton stays and increases the number of protons

by one.by one. The atomic number of the element increases by oneThe atomic number of the element increases by one The element changes into the next higher element on The element changes into the next higher element on

the periodic table.the periodic table. 100x stronger than an alpha particle100x stronger than an alpha particle

What happens to the numbers of particles in What happens to the numbers of particles in the nucleus after beta decay?the nucleus after beta decay?

Gamma Gamma RaysRays

An electromagnetic waveAn electromagnetic wave A packet of energyA packet of energy The energy readjustment in the nucleusThe energy readjustment in the nucleus Most powerful form of radiationMost powerful form of radiation The sun is a great source of gamma radiationThe sun is a great source of gamma radiation

Gamma Ray Photography From SpaceGamma Ray Photography From Space

AntoineAntoine Henri Henri BecquerelBecquerel

In 1896, radioactivity was In 1896, radioactivity was first discovered.first discovered.

Used uranium salts = placed Used uranium salts = placed them near a photographic them near a photographic film plate.film plate.

exposed the film exposed the film (below)(below)

Awarded Nobel Prize in Awarded Nobel Prize in 1903 in Physics1903 in Physics

Pierre & Marie CuriePierre & Marie Curie (1898) (1898)

Discover the radioactive properties of radium & poloniumDiscover the radioactive properties of radium & polonium Together awarded the Nobel Prize in 1903 (Together awarded the Nobel Prize in 1903 (physicsphysics) along ) along

with Henri Becquerelwith Henri Becquerel Marie is award a second Nobel Prize in 1911 (Marie is award a second Nobel Prize in 1911 (chemistrychemistry)) Pierre is killed in an accident in 1906, Marie continues Pierre is killed in an accident in 1906, Marie continues

working with radioactive substances.working with radioactive substances.

A small portion of Marie Curie’s Noble Prize A small portion of Marie Curie’s Noble Prize speech in 1911.speech in 1911.

““Some 15 years ago the radiation of uranium was Some 15 years ago the radiation of uranium was discovered by discovered by Henri BecquerelHenri Becquerel, and two years later , and two years later the study of this phenomenon was extended to other the study of this phenomenon was extended to other substances, first by me, and then by substances, first by me, and then by Pierre CuriePierre Curie and and myself. This study rapidly led us to the discovery of myself. This study rapidly led us to the discovery of new elements, the radiation of which, while being new elements, the radiation of which, while being analogous with that of uranium, was far more intense. analogous with that of uranium, was far more intense. All the elements emitting such radiation I have termed All the elements emitting such radiation I have termed radioactive, and the new property of matter revealed in radioactive, and the new property of matter revealed in this emission has thus received the name radioactivity.this emission has thus received the name radioactivity.

Thanks to this discovery of new, very powerful Thanks to this discovery of new, very powerful radioactive substances, particularly radium, the study radioactive substances, particularly radium, the study of radioactivity progressed with marvelous rapidity: of radioactivity progressed with marvelous rapidity: Discoveries followed each other in rapid succession, Discoveries followed each other in rapid succession, and it was obvious that a new science was in course of and it was obvious that a new science was in course of development.”development.”

TransmutationTransmutation

= changes from one element to another = changes from one element to another element during element during αα and and ββ decay. decay.

Alpha DecayAlpha Decay = mass number decreases = mass number decreases by 4 and the atomic number decreases by by 4 and the atomic number decreases by 22

Beta DecayBeta Decay = mass number does not = mass number does not change and the atomic number increases change and the atomic number increases by 1by 1

Alpha DecayAlpha Decay

Uranium-238 has 92 protonsUranium-238 has 92 protons

After alpha decay After alpha decay ((2 protons & 2 neutrons leave the nucleus2 protons & 2 neutrons leave the nucleus))

Becomes Thorium-234 and has 90 protonsBecomes Thorium-234 and has 90 protons

Beta DecayBeta Decay

Carbon-14 has 6 protons & 8 neutronsCarbon-14 has 6 protons & 8 neutrons

After beta decayAfter beta decay (a neutron is split into a proton and electron (a neutron is split into a proton and electron

& the electron is expelled from the nucleus)& the electron is expelled from the nucleus)

Becomes Nitrogen-14 and has 7 protons and 7 neutronsBecomes Nitrogen-14 and has 7 protons and 7 neutrons

Half LifeHalf Life

= the time it takes for one half of the mass of a = the time it takes for one half of the mass of a radioactive substance to decay.radioactive substance to decay.Ex: carbon-14 = 5730 yearsEx: carbon-14 = 5730 years

100 gram sample100 gram sample – In 5730 yrs = In 5730 yrs = 50 grams50 grams C-14 & C-14 & 50 grams50 grams N-14 N-14– In11,460 yrs = In11,460 yrs = 25 grams25 grams C-14 & C-14 & 75 grams75 grams N-14 N-14– In 17,190 yrs = In 17,190 yrs = 12.5 grams12.5 grams C-14 & C-14 & 87.5 grams87.5 grams N-14 N-14

Nuclear ReactionsNuclear Reactions

Nuclear FissionNuclear Fission

Nuclear FusionNuclear Fusion

Nuclear Fission

= the splitting of the nucleus into two smaller = the splitting of the nucleus into two smaller nucleinuclei

Neutrons are used to split the nucleusNeutrons are used to split the nucleus Additional neutrons are released to continue on Additional neutrons are released to continue on

to hit/split other nucleito hit/split other nuclei

Chain ReactionsChain Reactions

Critical MassCritical Mass ( (requiredrequired) = concentration of ) = concentration of radioactive atoms in a sample.radioactive atoms in a sample.Controlled Chain ReactionControlled Chain Reaction = many of the neutrons = many of the neutrons

that are produced are absorbed in “control rods” that are produced are absorbed in “control rods” prevent excess energy to be released.prevent excess energy to be released.

Ex. Nuclear Power PlantsEx. Nuclear Power Plants

Uncontrolled Chain ReactionUncontrolled Chain Reaction = all the neutrons = all the neutrons are allowed to continue to hit/split other nuclei are allowed to continue to hit/split other nuclei causing massive amounts of energy to be released causing massive amounts of energy to be released all at once.all at once.Ex. Atomic Bomb (used on Japan in 1945)Ex. Atomic Bomb (used on Japan in 1945)

Controlled Chain Controlled Chain ReactionReaction

Uncontrolled Chain Uncontrolled Chain ReactionReaction

Nuclear Fusion

= the joining of two smaller nuclei into a single = the joining of two smaller nuclei into a single larger nucleuslarger nucleus

Extremely more powerful release of energy Extremely more powerful release of energy than fissionthan fission

Requires a temperature of 10 million degrees Requires a temperature of 10 million degrees CelsiusCelsius

Also known as a Also known as a thermonuclear reactionthermonuclear reaction ex: H-bomb and the sun/starsex: H-bomb and the sun/stars

Fusion ExplosionsFusion Explosions

History of History of Chain Chain

ReactionsReactions The concept was first developed by The concept was first developed by Leó Szilárd in in

1933 which he then proceeded to get a patent on the 1933 which he then proceeded to get a patent on the concept the following year.concept the following year.

Leo Szilárd attempted to create a chain reaction using Leo Szilárd attempted to create a chain reaction using beryllium and and indium in 1936 but was unsuccessful. in 1936 but was unsuccessful.

The first artificial self-sustaining nuclear chain reaction The first artificial self-sustaining nuclear chain reaction was initiated by the was initiated by the Metallurgical Laboratory, led by , led by Enrico Fermi and Leó Szilárd, in a racquets court Enrico Fermi and Leó Szilárd, in a racquets court below the bleachers of Stagg Field at the University of below the bleachers of Stagg Field at the University of Chicago on December 2, 1942 during the Manhattan Chicago on December 2, 1942 during the Manhattan Project. (Project. (see link above to Einstein’s letter in 1939see link above to Einstein’s letter in 1939))

The Manhattan The Manhattan ProjectProject

September 1935: Nuremburg Laws begin severe persecution of Jews

March 1936: Occupation of the German Rhineland

July 1937: Japan invades China November 1937: The Axis Alliance is created by

a pact between Germany, Japan, and Italy March 1938: the Anschluss (occupation of Austria

by Germany) September 1938: German occupation of the

Sudetenland in Czechoslovakia

World War Breaks out in Europe in World War Breaks out in Europe in 19391939

Szilard drafted a letter in consultation with Albert Szilard drafted a letter in consultation with Albert Einstein that was addressed from Einstein to Einstein that was addressed from Einstein to President F.D. Roosevelt and which warned President F.D. Roosevelt and which warned him of the possibility of nuclear weapons (the him of the possibility of nuclear weapons (the "Einstein Letter"). "Einstein Letter").

This letter was delivered to FDR on October 11, This letter was delivered to FDR on October 11, 1939, and ten days later the first meeting of the 1939, and ten days later the first meeting of the Advisory Committee on Uranium (the "Briggs Advisory Committee on Uranium (the "Briggs Uranium Committee") was held in Washington, Uranium Committee") was held in Washington, DC on Pres. Roosevelt's order. DC on Pres. Roosevelt's order.

December 7, December 7, 19411941

USA Goes to WarUSA Goes to War official founding in August, the official founding in August, the

Manhattan ProjectManhattan Project reallyreally began on September 17, 1942began on September 17, 1942

Col. Leslie Richard GrovesCol. Leslie Richard Groves heads the project from the heads the project from the government’s endgovernment’s end

Groves asks Groves asks Dr. J. Robert Dr. J. Robert OppenheimerOppenheimer to head the to head the project from the scientists end.project from the scientists end.

““The Gadget”The Gadget”

Code NameCode Name = = TrinityTrinity

July 16, 1945 - At 5:29:45 July 16, 1945 - At 5:29:45 a.m. “a.m. “The GadgetThe Gadget” was ” was detonated in the first atomic detonated in the first atomic explosion in history. The explosion in history. The explosive yield was 20-22 explosive yield was 20-22 Kt, vaporizing the steel Kt, vaporizing the steel tower. tower.

TARGETSTARGETS??????

May 8, 1945 May 8, 1945 V-E DayV-E Day Germany surrenders Germany surrenders Japan now becomes the targetJapan now becomes the target Some scientists object to targeting Japan; the Some scientists object to targeting Japan; the

Nazis caused many of them to have to leave Nazis caused many of them to have to leave their homes and lost family members to the their homes and lost family members to the Holocaust. Holocaust.

August 6, 1945August 6, 1945

““Little Boy” is used on Little Boy” is used on Hiroshima, JapanHiroshima, Japan

Dropped from the B-29 Dropped from the B-29 bomber named “The Enola bomber named “The Enola Gay”Gay”

5 mile circle of destruction5 mile circle of destruction est. 78,000 killed & 70,000 est. 78,000 killed & 70,000

injured injured

August 9, August 9, 19451945

““Fat Man” is used on Fat Man” is used on Nagasaki, JapanNagasaki, Japan

2 mile circle of 2 mile circle of destructiondestruction

40,000 killed & 40,000 killed & 25,000 injured25,000 injured

Japan Japan unconditionally unconditionally surrenders a few surrenders a few days later & WWII is days later & WWII is officially overofficially over

VJ Day (VJ Day (Victory over JapanVictory over Japan) ) August 15, 1945August 15, 1945

Further Nuclear Further Nuclear DevelopmentsDevelopments

August 1949August 1949 = Soviet Union tests their first = Soviet Union tests their first atomic bomb after spies deliver US secret atomic bomb after spies deliver US secret bomb blue-printsbomb blue-prints

November 1952November 1952 = United States the first = United States the first Hydrogen bomb (H-bomb) 10 MT in strength, Hydrogen bomb (H-bomb) 10 MT in strength, USSR tests their first H-bomb in Aug. 1953USSR tests their first H-bomb in Aug. 1953

Other Atomic weapons countries include Great Other Atomic weapons countries include Great Britain, China, France, India, Pakistan, and Britain, China, France, India, Pakistan, and possibly Israel. North Korea and Iran are possibly Israel. North Korea and Iran are currently in the news for seeking nuclear currently in the news for seeking nuclear capabilities.capabilities.