Chapter 18 Nuclear Reactions

Chemical Reactions  Occur in the outer electron energy level  Valance electrons  Ionic or covalent bonding occurs

Nuclear Reactions  Occur in the nucleus of the atom  Involve the NUCLEONS  Nucleons = protons & neutrons  Transmutation occurs

Strong Nuclear Force  Protons are positively charged and repel each other  ←+ +→  Strong Nuclear Force = the force that causes the protons and neutrons in the nucleus to stick together and holds the nucleus tightly together.

ISOTOPES  Atoms of the same element with a different number of neutrons.  Ex: carbon-12 & carbon-14  Carbon-12  6 protons  6 neutrons  6 electrons  Carbon-14  6 protons  8 neutrons  6 electrons

3 Types of Radioactivity Radioactive Decay  ALPHA PARTICLE ( α )  BETA PARTICLE ( β )  GAMMA RAYS ( γ )

ALPHA PARTICLE  2 protons & 2 neutrons  nucleus of a helium atom  weakest type of radiation  12 inches max. distance travel

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

BETA PARTICLE  an electron emitted from the nucleus  A neutron splits into a proton & electron  The electron is expelled out of the nucleus  The proton stays and increases the number of protons by one.  The atomic number of the element increases by one  The element changes into the next higher element on the periodic table.  100x stronger than an alpha particle

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

Gamma Rays  An electromagnetic wave - packet of energy  A The energy readjustment in the nucleus  Most powerful form of radiation  The sun is a great source of gamma radiation  DANGEROUS to living organisms

Stopped by: alpha – paper/skin beta – wood gamma – several feet of concrete/lead

Gamma Ray Photography From Space

Antoine Henri Becquerel  In 1896, radioactivity was first discovered.  Used uranium salts = placed them near a photographic film plate.  exposed the film (below)  Awarded Nobel Prize in 1903 in Physics

Pierre & Marie Curie (1898)  Discover the radioactive properties of radium & polonium  Together awarded the Nobel Prize in 1903 (physics) along with Henri Becquerel  Marie is award a second Nobel Prize in 1911 (chemistry)  Pierre is killed in an accident in 1906, Marie continues working with radioactive substances.

Transmutation  = changes from one element to another element during α and β decay.  Alpha Decay =  mass number decreases by 4  atomic number decreases by 2  Beta Decay =  mass number does not change  atomic number increases by 1

Alpha Decay  Uranium-238 has 92 protons  After alpha decay (2 protons & 2 neutrons leave the nucleus)  Becomes Thorium-234 and has 90 protons

Beta Decay  Carbon-14 has 6 protons & 8 neutrons  After beta decay (a neutron is split into a proton and electron & the electron is expelled from the nucleus)  Becomes Nitrogen-14 and has 7 protons and 7 neutrons

Half Life = the time it takes for one half of the mass of a radioactive substance to decay. Ex: carbon-14 = 5730 years 100 gram sample –In 5730 yrs = 50 grams C-14 & 50 grams N-14 –In11,460 yrs = 25 grams C-14 & 75 grams N-14 –In 17,190 yrs = 12.5 grams C-14 & 87.5 grams N-14

Nuclear Reactions  Nuclear Fission  Nuclear Fusion

Nuclear Fission Nuclear Fission  = the splitting of the nucleus into two smaller nuclei  Neutrons are used to split the nucleus  Additional neutrons are released to continue on to hit/split other nuclei

Chain Reactions  Critical Mass ( required ) = concentration of radioactive atoms in a sample.  Controlled Chain Reaction = many of the neutrons that are produced are absorbed in “control rods” prevent excess energy to be released. Ex. Nuclear Power Plants  Uncontrolled Chain Reaction = all the neutrons are allowed to continue to hit/split other nuclei causing massive amounts of energy to be released all at once.  Ex. Atomic Bomb (used on Japan in 1945)

Controlled Chain Reaction

Uncontrolled Chain Reaction

Nuclear Fusion Nuclear Fusion  = the joining of two smaller nuclei into a single larger nucleus  Extremely more powerful release of energy than fission  Requires a temperature of 10 million degrees Celsius  Also known as a thermonuclear reaction  ex: H-bomb and the sun/stars

Fusion Explosions

History of Chain Reactions  The concept was first developed by Leó Szilárd in 1933 which he then proceeded to get a patent on the concept the following year. Leó SzilárdLeó Szilárd  Leo Szilárd attempted to create a chain reaction using beryllium and indium in 1936 but was unsuccessful. berylliumindium berylliumindium  The first artificial self-sustaining nuclear chain reaction was initiated by the Metallurgical Laboratory, led by Enrico Fermi and Leó Szilárd, in a racquets court below the bleachers of Stagg Field at the University of Chicago on December 2, 1942 during the Manhattan Project. ( see link above to Einstein’s letter in 1939 ) Metallurgical Laboratory Enrico FermiStagg FieldUniversity of ChicagoManhattan ProjectMetallurgical Laboratory Enrico FermiStagg FieldUniversity of ChicagoManhattan Project

The Manhattan Project   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 1939 Szilard drafted a letter in consultation with Albert Einstein that was addressed from Einstein to President F.D. Roosevelt and which warned him of the possibility of nuclear weapons (the "Einstein Letter"). Einstein LetterEinstein Letter This letter was delivered to FDR on October 11, 1939, and ten days later the first meeting of the Advisory Committee on Uranium (the "Briggs Uranium Committee") was held in Washington, DC on Pres. Roosevelt's order.

December 7, 1941

USA Goes to War  official founding in August, the Manhattan Project really began on September 17, 1942  Col. Leslie Richard Groves heads the project from the government’s end  Groves asks Dr. J. Robert Oppenheimer to head the project from the scientists end.

“The Gadget”

Code Name = Trinity  July 16, At 5:29:45 a.m. “The Gadget” was detonated in the first atomic explosion in history. The explosive yield was Kt, vaporizing the steel tower.

TARGETS ???  May 8, 1945 V-E Day Germany surrenders  Japan now becomes the target  Some scientists object to targeting Japan; the Nazis caused many of them to have to leave their homes and lost family members to the Holocaust.

August 6, 1945  “Little Boy” is used on Hiroshima, Japan  Dropped from the B-29 bomber named “The Enola Gay”  5 mile circle of destruction  est. 78,000 killed & 70,000 injured

August 9, 1945  “Fat Man” is used on Nagasaki, Japan  2 mile circle of destruction  40,000 killed & 25,000 injured  Japan unconditionally surrenders a few days later & WWII is officially over

VJ Day ( Victory over Japan ) August 15, 1945

Further Nuclear Developments  August 1949 = Soviet Union tests their first atomic bomb after Russian spies delivered US secret bomb blue-prints  November 1952 = United States the first Hydrogen bomb (H-bomb) 10 MT in strength, USSR tests their first H-bomb in Aug  Other Atomic weapons countries include Great Britain, China, France, India, Pakistan, and possibly Israel.

North Korea & Iran are currently in the news for seeking nuclear capabilities. What is the problem with these counties having nuclear weapons? North Korea = violation of the treaty to end the Korean War. North Korea = violation of the treaty to end the Korean War. Iran = violation of a United Nations Resolution Iran = violation of a United Nations Resolution BOTH WOULD/COULD BE CONSIDERED ACTS OF WAR!!!