Flashcard Set Preview
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| 1 |
atoms
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term that means cannot be divided
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matter
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early scientists knew matter was made up of timy particles but did not have equipment to prove...
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element
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substance that cannot be broken down into a simpler substance
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John Dalton
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....matter is made up of atoms.... atoms cannot be divided into smaller pieces....all atoms...
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William Crookes
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did experiments with electrodes(metal that can conduct electricity)in a glass tube with almost...
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anode
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electrode with a + charge
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cathode
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electrode with a - charge
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Crookes saw a shadow of a cross - shaped object in the tube and determined it was charged particles...
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Crookes knew it couldn't be light because light does not bend by a magnet so it had to be negatively...
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How did Crookes know the particles were negatively charged??
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because opposite charges attract and these were attracted to the + charged anode
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cathode-ray tube
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the tube from Crookes experiment and the tube which started development of t.v. and computer...
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J.J. Thomson
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he did not believe Crookes so he did the same experiment using different metals for the cathodes...
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Thomson found...
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the same negatively charged particles were produced
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Thomson concluded....
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that cathode rays are negatively charged particles of matter now called...electrons
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Electrons...
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are part of every kinds of atom because they are produced by every kind of cathode material
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Thomson also found...
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atoms can be divided into smaller particles
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Ernest Rutherford
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Rutherford hypothesized that the protons of an atom were found in a very small space at the...
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Neutrons
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no charge(neutral)found in the nucleus
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Protons
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positively charged..found in the nucleus
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Electrons
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negatively charged...found outside the nucleus in electron cloud...electrons are in constant...
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Atomic number
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the # of protons in the nucleus
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# neutrons
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atoms of the same element can have the same # of protons and neutrons OR different #...
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Isotopes
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atoms of the same element that have different numbers of neutrons..see table on page 48
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Mass #
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# of neutrons + # of protons
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# neutrons
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atomic # - mass #
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strong nuclear force
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neutrons in nucleus help keep protons apart so they do not repel each other....(protons are...
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Finding # of protons, neutrons, and electrons summary
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...# protons = atomic #(found on chart at the top...# electrons = # of protons...mass # found...
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EX: Cobalt 27 ...
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#protons = 27# electrons = 27mass # = 58.933# neutrons = 58.933 - 27 which is 31.933
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radioactive decay
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Some nuclei are unstable due to having too many or too few neutrons--especially in heavier...
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transmutation
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When particles are ejected from the nucleus, the atomic number of the nucleus can change. One...
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smoke alarms
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work through transmutation by ejecting an alpha particle (2 protons & 2 neutrons)
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half-life
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the amount of time it takes for half of a sample of an element to decay.
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Carbon dating
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carbon 14 is used to deterine the age of dead animals, plants, and humans.
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half-life of c-14
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5730 years
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C-14
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in living organism the amount of c-14 remains the same with the levels c-14 in the atmosphere...
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while living...
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any c-14 nucleus that decays is replaced by another from the environment
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when the organism dies...
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the c-14 cannot be replaced.
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when the organism is found...
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scientists compare how much c-14 it has to how much it would have had when it was alive.
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radioactive waste
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waste products from nuclear power plants. The plants produce left over isotopes that release...
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| 39 |
radioactive waste sites..
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radioactive waste is buried in special containers at a site in Carlsbad, N.M.
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Transmutation produces...
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new elements..
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tracer elements
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used to diagnose disease and study environment,
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how tracer elements work..
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a radioactive isotope is put into a living organism(thyroid)and followed as it decays by a...
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mutation
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a change
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