Unit #1-Atomic Structure

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Atomos
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greek word for atom- means not able to be divided
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Democritus
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Greek philosopher who developed an atomistic theory of matter (460-370 BC)
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atom
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(physics and chemistry) the smallest component of an element having the chemical properties of the element
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Dalton’s Atomic Theory
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1) elements are composed of atoms. 2) atoms of same element are identical, but differ from other elements. 3) elements can mix together 4) atoms only change when mixed with other elements
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J J Thomson
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Discovered the electron
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Plum Pudding Model of the atom
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atoms are balls of positively charged material with negative electrons scattered throughout
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Electron
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negatively charged particle; located outside the atomic nucleus
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Cathode-ray tube
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evacuated glass tube in which a stream of electrons emitted by a cathode strikes a fluorescent material, causing it to glow
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Ernest Rutherford
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British physicist (born in New Zealand) who discovered the atomic nucleus and proposed a nuclear model of the atom (1871-1937)
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Gold Foil experiment
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Conducted by Ernest Rutherford in which alpha particles that were shot at gold foil were deflected when they hit the positive center of gold atoms. The nucleus was discovered as a result of this experiment.
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Nuclear model of the atom
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created by Ernest Rutherford. Replaced the Plum Pudding Model. Atom is like a miniature solar system with the positive particles in the middle and the negative particles orbiting as the planets do around the center.
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Proton
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a subatomic particle that has a positive charge and that is found in the nucleus of an atom
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Nucleus
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the positively charged dense center of an atom
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James Chadwick
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Discovered the neutron
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Neutron
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a subatomic particle that has no charge and that is found in the nucleus of an atom
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Electromagnetic force
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the attraction or repulsion between charged particles. electromagnetic force holds negatively charged electrons to the positively charged nuclei of atoms.
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Strong nuclear force
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a powerful force of attraction that acts only on the neutrons and protons in the nucleus, holding them together
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N. Bohr
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provided the modern concept of the atomic model (1940)
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Bright line spectra
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Light emitted by an excited element is passed through a prism or diffraction grating
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Bohr Model
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model of the atom in which electrons move rapidly around the nucleus in paths called orbits
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Picometer(pm)
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a metric unit of length equal to one trillionth of a meter
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Atomic number (Z)
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the number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element
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Mass number (A)
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the sum of the number of protons and neutrons in the nucleus of an atom
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Isotope
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atoms of the same element that have different numbers of neutrons
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Protium
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the simplest form of hydrogen that contains 1 proton and no neutrons in the nucleus; the nucleus is surrounded by 1 electron
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Deuterium
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An isotope of hydrogen that contains one proton and one neutron per atom.
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Tritium
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An isotope of hydrogen that contains one proton and two neutrons per atom.
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Relative Atomic Mass
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(chemistry) the ratio of the atomic mass of an element to half the atomic mass of carbon-12
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Atomic Mass Unit (amu)
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A unit used to measure the mass of particles in atoms; a proton or neutron has a mass of 1 amu.
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Average Atomic Mass
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the weighted average of the masses of all naturally occurring isotopes of an element
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Mole
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the molecular weight of a substance expressed in grams
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Avogadro’s number
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number of representative particles in a mole, 6.02 X 10^23
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Molar mass
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the mass of one mole of a pure substance
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Scanning Tunneling Microscope (STM)
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an instrument that generates images of surfaces at the atomic scale
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Nucleon
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any particle present in the nucleus of an atom, that is, a proton or neutron.
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Nuclide
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An atom that is identified by the number of protons and neutrons in its nucleus, The general term for any isotope of any element; another term for an atom that is identified by the number of protons and neutrons in its nucleus
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Mass defect
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the difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons
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Albert Einstein
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physicist born in Germany who formulated the special theory of relativity and the general theory of relativity
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E=mc^2
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Einstein’s equation proposing that energy has mass; E is energy, m is mass, and c is the speed of light
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Quark
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hypothetical truly fundamental particle in mesons and baryons
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Murray Gell-Mann
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American physicist. In 1963 he and George Zweig independently postulated the existence of quarks. He was awarded the 1969 Nobel Prize in physics.
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Nuclear Reaction
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(physics) a process that alters the energy or structure or composition of atomic nuclei
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Henri Becquerel
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French physicist who discovered that rays emitted by uranium salts affect photographic plates (1852-1908)
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Marie and Pierre Curie
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Marie (1867-1934) a polish born physicist, and her husband Pierre discovered that radium constantly emits subatomic particles, which means it doesn’t have a constant weight.
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Radioactive decay
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the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation
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Alpha emission
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radioactive decay of a nucleus that is accompanied by emission of alpha particles
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Alpha particle
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a positively charged particle that is the nucleus of the helium atom
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Beta emission
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release of an electron from the nucleus
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Beta particle
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a high-speed electron or positron emitted in the decay of a radioactive isotope
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Positron emission
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a radioactive decay process in which a proton in the nucleus in converted into a neutron and a positron and then the positron is emitted from the nucleus
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Positron
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A particle with the mass of an electron but a positive charge
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Electron capture
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the process in which an inner orbital electron is captured by the nucleus of the atom that contains the electron
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Gamma rays
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Electromagnetic waves with the shortest wavelengths and highest frequencies
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Half-life
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length of time required for half of the radioactive atoms in a sample to decay
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Particle accelerator
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a machine that moves atomic nuclei at higher and higher speeds until they crash into one another, sometimes forming heavier elements
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Large Hadron Collider
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Particle Accelerator constructed beneath Geneva.
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Transuranium elements
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the elements in the periodic table with atomic numbers above 92, which all undergo transmutation
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Roentgen (R)
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a unit of radiation exposure descriptive of x or gamma radiation, the quantity of which would produce a charge
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rem
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(Roentgen Equivalent Man) the dosage of ionizing radiation that will cause the same amount of injury to human tissue as 1 roentgen of X-rays
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Geiger-counter
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radiation detector that produces a click or a flash of light when a charged particle is detected
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Radioactive dating
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technique in which scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains
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Radioactive tracer
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a radioactive atom that is incorporated into a substance so that movement of the substance can be followed by a radiation detector
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Nuclear fission
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a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy
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Nuclear fusion
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a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy
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Manhattan Project
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code name for the secret United States project set up in 1942 to develop atomic bombs for use in World War II
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Enrico Fermi
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Italian nuclear physicist (in the United States after 1939) who worked on artificial radioactivity caused by neutron bombardment and who headed the group that in 1942 produced the first controlled nuclear reaction (1901-1954)
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Chain reaction
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a series of chemical reactions in which the product of one is a reactant in the next
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Trinity, New Mexico
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Place where first atomic bomb was tested
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Los Alamos National Labs
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Site of the Manhattan Project HQ. Place of Atomic Bomb’s invention.
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Robert Oppenheimer
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an American theoretical physicist, best known for his role as the director of the Manhattan Project, the World War II effort to develop the first nuclear weapons, at the secret Los Alamos laboratory in New Mexico. Known as “the father of the atomic bomb,” at the Trinity test, he said, quoting from the Bhagavad Gita, “If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one. Now I am become Death, the destroyer of worlds.”
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Hiroshima
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City in Japan, the first to be destroyed by an atomic bomb, on August 6, 1945. The bombing hastened the end of World War II. (p. 797)
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Nagasaki
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Japanese city in which the second atomic bomb was dropped (August 9, 1945).
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Critical mass
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the minimum mass of fissionable material that can sustain a chain reaction
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Chernobyl
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nuclear power plant in Russia that had an explosion in 1986 & released radioactive materials into the air
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Three-Mile Island
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1979 – A mechanical failure and a human error at this power plant in Pennsylvania combined to permit an escape of radiation over a 16 mile radius.
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***ushima
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When the earthquake hit, the nuclear reactors all automatically shutdown. Within seconds after the earthquake started, the control rods had been inserted into the core and the nuclear chain reaction stopped. At this point, the cooling system has to carry away the residual heat, about 7% of the full power heat load under normal operating conditions. The earthquake destroyed the external power supply of the nuclear reactor. This is a challenging accident for a nuclear power plant, and is referred to as a “loss of offsite power.” The reactor and its backup systems are designed to handle this type of accident by including backup power systems to keep the coolant pumps working. Furthermore, since the power plant had been shut down, it cannot produce any electricity by itself. For the first hour, the first set of multiple emergency diesel power generators started and provided the electricity that was needed. However, when the tsunami arrived (a very rare and larger than anticipated tsunami) it flooded the diesel generators, causing them to fail. After they failed the reactor operators switched to emergency battery power. The batteries were designed as one of the backup systems to provide power for cooling the core for 8 hours. And they did. After 8 hours, the batteries ran out, and the residual heat could not be carried away any more. At this point the plant operators begin to follow emergency procedures that are in place for a “loss of cooling event.”
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Uranium-235
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an unstable, fissionable isotope of uranium
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Plutonium-239
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a radioactive isotope produced in a breeder reactor and used as a nuclear fuel
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Richard Feynman
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United States physicist who contributed to the theory of the interaction of photons and electrons (1918-1988)
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Lise Meitner
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Swedish physicist (born in Austria) who worked in the field of radiochemistry with Otto Hahn and formulated the concept of nuclear fission with Otto Frisch (1878-1968)

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