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24 Cards in this Set
- Front
- Back
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Democritus |
4th century BCE; proposed that all matter was composed of tiny, invisible solid particles or atoms |
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John Dalton |
In 1807 proposed an atomic model: indivisible, solid, spheres of uniform density |
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William Crookes |
Late 1800s he built a cathode ray tube: high V across low P gases; glow was found to be charged particles since magnets deflected them |
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Cathode Rays |
Cathode rays or electrons are released from the - electrode of a cathode ray tube |
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Electrode |
- or + (cathode or anode) charged conductor |
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Cathode Ray Tube (CRT) |
Sealed tube with high V electrodes and low P gas |
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J.J. Thomson |
1897 modified Crookes' tube to include a fluorescent screen; found the charge: mass ratio of cathode rays or electrons; Plum Pudding model of atom |
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Ernest Rutherford |
1911 interpreted his Gold Foil experiment results to form the Planetary Model of the atom |
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Radioactivity |
Emissions of alpha and beta particles and gamma rays from the nuclei of certain unstable atoms |
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Alpha particle |
2 protons and 2 neutrons held together; penetrates sheet of paper |
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Subatomic particles |
Particles within atoms: protons, electrons, neutrons |
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Nucleus |
Tiny core of atom composed of protons and neutrons |
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Proton |
+ charged particle in the nucleus; responsible for atomic properties |
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Neutron |
Neutral particle in the nucleus |
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Electron |
- charged particle orbiting the nucleus |
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Atomic number |
Equal to # of protons in an atom |
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Mass number |
Sum of protons and neutrons |
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Isotope |
A form of an atom which differs in # of neutrons from other isotopes |
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Atomic mass |
Average mass of all isotopes, based on % abundance in nature |
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amu |
Atomic mass unit; approximately equal to mass of 1 proton or 1 neutron |
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Niels Bohr |
1913 explained the line of spectra of H2 in terms of atom's electrons energy levels |
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Emission spectrum |
Spectrum emitted by objects eg. Line spectra of gases |
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Line spectrum |
A set of distinct coloured lines (separated by blackness) unique for each element; spectra can be observed with a device called a spectroscope |
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Continuous line spectrum |
(Incandescent) glow produced by heated solids |
