Unit #1 Atomic Structure Vocab

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atomos
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greek word for atom- means not able to be divided
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Democritis
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Discovered “small indivisible particles” that he named atoms.
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Atom
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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 Thompson
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used the cathode ray tube to discover 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 throught
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Electron
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a subatomic particle that has a negative charge
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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.
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Ernest Rutherford
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British physicist who discovered the atomic nucleus and proposed a nuclear model of the atom
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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. 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 stable particle with positive charge equal to the negative charge of an electron
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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 in 1932
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Neutron
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an elementary particle with 0 charge and mass about equal to a proton
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Electromagnetic force
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the attraction or repulsion between charged particles. electromagnetic force holds electrons to the 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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Neils Bohr
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a Danish physicist created a new atomic model in 1922; described electrons as moving around the nucleus in fixed orbits and having a set amount of energy (planetary model)
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Bright line spectra
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the unique amounts of energy emitted as electrons return to the ground state, specific colors shown as individual bright lines
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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 common unit of length; 1 pm = 10^-12 m
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Atomic number (Z)
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The number of protons in the nucleus of an atom.
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Mass number (A)
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the sum of the number of protons and neutrons in the nucelus of an atom
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Isotope
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one of two or more atoms with the same atomic number but with 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
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Deuterium
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an isotope of hydrogen which has one neutron (as opposed to zero neutrons in hydrogen)
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Tritium
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a radioactive isotope of hydrogen
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Relative atomic mass
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the ratio of the atomic mass of an element to half the atomic mass of carbon-12
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Atomic mass unit
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unit of mass for expressing masses of atoms or molecules
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Average atomic mass
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weighted average of the atomic masses for the 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 in grams of 1 mole of a 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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a constituent (proton or neutron) of an atomic nucleus
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Nuclide
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A general term for a specific isotope of an element
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Mass defect
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the amount by which the mass of an atomic nucleus is less than the sum of the masses of its constituent particles
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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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very small particles of matter that make up protons and neutrons
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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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A process that alters the energy or structure or composition of atomic nuclei
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Henri Becquerel
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A French Scientist whose discovery was radioactivity which occurs when a nucleus has too many or too few neutrons in ratio to its number of protons
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Marie and Pierre Curie
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French chemist (born in Poland) who won two Nobel prizes; one (with her husband and Henri Becquerel) for research on radioactivity and another for her discovery of radium and polonium (1867-1934))
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Radioactive decay
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the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
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Alpha emission
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radioactive decay of an atomic nucleus that is accompanied by the emission of an alpha particle.
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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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When a beta particle (electron like particle) is ejected from the nucleus; this release causes a neutron to convert into a proton.
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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 is 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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Radioactive process in which a nucleus captures an inner-shell electron that combines with a proton to form a neutron. As a result, the atomic number decreases by 1, but the atomic mass remains the same.
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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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the time required for one half of the atoms of a radioisotope to emit radiation an decay products
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Particle accelerator
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A machine that moves atomic nuclei at high speeds until they crash into one another, forming heavier elements
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Large Hadron Collider (LHC)
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Gigantic scientific instrument. Particle accelerator. Used to study smallest known particles.
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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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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 Counters
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instruments that detect radiation by counting electric pulses carries by a gas ionized by radiation
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Radioactive Tracer
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A radioactive material that is added to a substance so that its distribution can be detected later.
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Radioactive Dating
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measurement of the amount of radioactive material (usually carbon 14) that an object contains
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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 the atomic bomb 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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United States physicist who directed the project at Los Alamos that developed the first atomic bomb (1904-1967)
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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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The nuclear power plant in the Ukraine that suffered two large explosions which released massive amounts of radioactive materials. It is the worst nuclear accident in history and thousands were and continue to be impacted by the disaster.
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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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Fukushima
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Where the latest nuclear power plant disaster occured in Japan. An Earthquake caused all the power plants to shut down.
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Uranium-235
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a uranium isotope with mass number 235
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Plutonium-239
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a highly fissionable isotope of plutonium that is used in atomic weapons and as a reactor 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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