Chapter 18 Nuclear Reactions
Chapter 18Nuclear Reactions
Chemical Reactions
Occur in the outer electron energy levelValance 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 RadioactivityRadioactive Decay
ALPHA PARTICLE (α)
BETA PARTICLE (β)
GAMMA RAYS (γ)
ALPHA PARTICLE2 protons & 2 neutronsnucleus of a helium atomweakest type of radiation12 inches max. distance travel
What happens to the numbers of particles in the nucleus after alpha decay?
BETA PARTICLE
an electron emitted from the nucleusA neutron splits into a proton & electronThe 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 energyA The energy readjustment in the nucleusMost powerful form of radiationThe sun is a great source of gamma radiationDANGEROUS 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
= the splitting of the nucleus into two smaller nuclei
Neutrons are used to split the nucleusAdditional 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
= 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 reactionex: 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.
Leo Szilárd attempted to create a chain reaction using beryllium and indium in 1936 but was unsuccessful.
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)
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").
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 Warofficial 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, 1945 - At 5:29:45 a.m. “The Gadget” was detonated in the first atomic explosion in history. The explosive yield was 20-22 Kt, vaporizing the steel tower.
TARGETS???
May 8, 1945 V-E Day Germany surrendersJapan now becomes the targetSome 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 destructionest. 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. 1953
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.
• Iran = violation of a United Nations Resolution
BOTH WOULD/COULD BE CONSIDERED ACTS OF WAR!!!