atomic structure and nuclear chemistry

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democritus
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all matter is made out of tiny, indivisible particles (atomos). no experimentation, no explanation of chemical behavior.
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aristotle
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did not believe in atoms. All matter is continuous, composed of air, water, fire and earth. his;refs weren’t challenged until the age of experimentation in the 18th century.
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john dalton
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proposed an atomic theory based on experimentation, observed that elements combine in simple, whole number ratios, meaning that the smallest piece of the combining elements had to a particle (atom)
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dalton’s atomic theory
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1) elements are composed of tiny, indivisible particles called atoms 2) atoms of the same element are identical, and different from atoms of any other element. 3) atoms of different elements can be mixed together, or they can chemically combine with atoms of another elements in simple, whole number ratios to form compounds. (law of Definite Proportions) 4) atoms of one element can never change into atoms of another element.
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JJ thompson
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cathode ray tube experiments. named the particle an electron, did not depend on the type of gas, therefore they were in all elements. Plum pudding. (bulk was positive, electrons dispersed like raisins)
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cathode ray tube experiment
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jj thompson- passed an electric current through gases at a low pressure, the resulting “rays” were attracted to the positive plate, so they must be negatively charged.
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Robert Millikan
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oil drop experiment determined the mass and charge of the electron.
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ernest rutherford
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“father of nuclear physics” proved that alpha radiation was a stream of helium nucleii. gold foil experiment: atoms must be mostly empty space. positive charge and mass concentrated on the nucleus. discovered the proton
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gold foil experiment
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directed a beam of alpha particles at thin gold foil. most went straight through, a few were deflected
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niels bohr
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planetary model of the atom, nucleus was the center and electrons orbit around it. electrons move in discreet energy levels.
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james chadwick
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discovered the neutron
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quantum theory
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electrons do not orbit the nucleus like planets electrons do exist in discreet energy levels, defined by regions of probability it is impossible to determine the exact location of an electron at any time most of the mass is in the nucleus
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protons
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P+, charge: +1, relative mass: 1u, found in the nucleus
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electrons
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E-, charge: -1, relative mass: 0u, found in energy levels (“shells”) around the nucleus
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neutron
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N^0, charge: 0, relative mass: 1u, found in the nucleus
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atomic number
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# of protons = # of electrons in a neutral atom
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mass number
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# of protons + # of neutrons (always a whole number bc it counts particles)
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isotope
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atoms of the same element that have different masses. # of protons is the same and # of neutrons is different.
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protium-1
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hydrogen isotope 1 protron, 0 neutrons, mass # 1
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deuterium-2
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1 proton, 1 neutron, mass # 2
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tritium
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1 proton, 2 neutrons, mass # 3
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hyphen notation
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“hydrogen-3”
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symbol notation
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“^3H”
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relative atomic mass
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atomic mass unit (AMU) or u, based on the isotope carbon-12. 1 amu = 1/12 the mass of carbon-12 atom.
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average atomic mass
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a weighted average of al the isotopes of the element. the mass listed on the periodic table. (rarely a whole number)
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relative abundance
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percentage of this isotope found on earth compared to other isotopes of the same element
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andre henri
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discovered radioactivity when he observed that uranium emitted radiation without an external source of energy.
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marie and pierre curie, becquerel
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won the nobel prize in physics
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radioactivity
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the process by which an atomic nuclear gives off radiation
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radiation
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penetrating rays emitted by a radioactive source.
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radioisotopes
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unstable nucleii, loses energy by spontaneously emitting radiation.
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radioactive decay
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an unstable nucleus spontaneously emitting radiation, ne way transmutation
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nuclide
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an atom of an isotope
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stable nuclides
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always have at least as many neutrons as protons odd/odd are unstable except for hydrogen-2, boron-10, lithium-6, and nitrogen-14 all nuclides with atomic number greater than or equal to 84 are unstable
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alpha emission
alpha emission
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the atom loses an e=alpha particle: helium nuclei 2 protons, 2 neutrons, charge: +2 atomic number decreases by 2 and mass number decrease by 4 don’t travel far bc of mass most dangerous if ingested stopped by paper
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beta emission
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fast moving electrons formed when a neutron decomposes into a proton and an electron. ejected electron. atomic number increases by 1, mass stays the same charge: -1 smaller, more penetrating than alpha particles, stop by aluminum foil, thin wood and lead
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gamma emission
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high energy electromagnetic radiation emitted from a nucleus as it changes from an excited state to a ground energy state. no charge or mass extremely penetrating, stopped by lead, concrete
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radioactive series (decay chain)
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the decay of a radioactive isotope into other radioactive isotopes through a series of alpha, beta or gamma emissions. will continue until a stable isotope is found.
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parent nuclide
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heaviest nuclide in the series
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daughter nuclide
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the nuclide produced by the decay of the parent
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3 natural decay series
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uranium-238, uranium-235, and thorium-232
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uranium-235
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first five steps in decay: a, b, a, a, b
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positron emission
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a particle with the mass of an electron but with a positive charge, formed when the proton changes into a neutron. occurs when neutron;proton ratio is too small. atomic number decreases by 1 (1 less proton), mass doesn’t change charge: +1 stopped by lead
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electron capture
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an inner orbital electron is captured by the nucleus of its own atom, combines with a proton, and forms and neutron. k-capture. atomic number decreases by 1 (proton to neutron), mass stays the same
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nuclear transmutation
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occurs when a nuclear reaction transforms an isotope of one element into the isotope of another element.
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nuclear bombardment
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occurs when high energy particles (protons, neutrons, alpa particles) bombard the nucleus of an atom
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particle accelerators
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accelerate the bombarding particles to speeds close to the speed of light by use of electromagnetic fields
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transuranium elements
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elements with an atomic number > 92 none occur in nature all are radioactive synthesized in nuclear rectors and particle accelerators
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half life
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time required for half the atoms of a radioactive nuclide to decay symbol: t1/2 the longer the half-life, the more stable the isotope
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carbon-14
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t1/2= 5730 years all living things go through the carbon cycle when an organism dies, the amount of carbon-14 begins to decline as it decays an is not replenished by a living organism beta emission
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uranium-238
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t1/2=4.5×10^9 years
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decimal fraction of radioactive atoms remaining
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1/2n, where n = number of half lives
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number of half lives elapsed
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total time elapsed/length of half-life
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remaining mass of an isotope
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(initial mass of an isotope)x (decimal amount remaining)
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fusion
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occurs when two light nucleic combine to produce a nucleus of heavier mass, accompanied by the release of a large amount of energy. occurs in all stars high temps required products mostly stable possible energy source
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hydrogen bomb
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occur due to the fusion of two deuterium nuclei, initiated by the detonation of a fission bomb.
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fission
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occurs when isotopes are bombarded with neutrons splits the nucleus into smaller fragments releases neutrons and large amount of energy can be controlled heat used to generate steam to drive a turbine, spinning turbine provides electricity.
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suitable coolant
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removes energy given off as heat from the reactor core
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neutron moderation
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water or carbon slows down neutrons so they can be captured by the reactor fuel to continue the chain reaction.
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neutron absorption
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rods made of some type of neutron-absorbing material (usually cadmium) are extended into the rector o pulled out of the reactor to control the rate of fission into=absorb neutron=slows down out=absorb fewer neutron=speeds up
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methods of detecting radiation
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geiger counter scintillation counter film badge
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geiger counter
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primarily beta
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scintillation counter
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coated screen detect radiation particles
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film badge
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several layers of photographic film encased in a holder. detect beta and gamma
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radioisotopes in medicine
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imaging soft-tissue organs special detectors are placed around the body after radioisotopes are administered to detect gamma radiation tomography half life requirements: should use lowest dose with shortest half-life. longer half-lives prevent reducing too often (tumor treatment) tracers
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tomography
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computer analysis of information, 3D image of the organ
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tracers
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iodine-131 : used to check for thyroid cancer cobalt-60 and cesium-137: radiation sources for cancer treatment

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