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64 Cards in this Set
- Front
- Back
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Particle theory
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by Democritus; all matter consists of small, indivisible particles
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Aristotle's view on matter
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continuous, composed of a single substances (hyle)
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Lavoisier
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Law of Conservation and Mass
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Law of Conservation and Mass
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mass is neither created nor destroyed
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Proust
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Law of Definite Proportions
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Law of Definite Proportions
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specific substances always contain elements in the same ratio by mass
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Dalton
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Law of Multiple Proportions
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Law of Multiple Proportions
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if two or more different compounds are composed of the same two elements, the ratio of masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers
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Cathode ray tube
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evacuated glass tube with 2 metal electrodes
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Cathode
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negative electrode
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Anode
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positive electrode
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Cathode Ray
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stream of electrons that travel from cathode to anode; cause the tube to glow
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What did experiments of the cathode ray tube show?
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showed that rays were deflected by a magnetic field and away from a negatively charged plate
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Thomson
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noted for discovery of electron; found the charge to mass ratio; found that electrons had a negative charge
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Millikan
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conducted Oil Drop Experiment
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Significance of Oil Drop Experiment
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confirmed that electrons are negatively charged, calculated the charge on electron
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What discovery did the knowledge of electrons lead to?
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that there must be a positive charge to balance negative electrons; atoms must contain other particles
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How were the oil drops controlled?
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kept the same, rose, or fell
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Rutherford
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Gold Foil Experiment, "planetary model"
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Gold Foil Experiment
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alpha particles bombarded thin gold foil
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Modern atomic theory
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1) different kinds of atoms (isotopes), 2) atoms can be destroyed by nuclear reactions
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Thomson's plum pudding model
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sphere filled with fluid (pudding), had electrons (plums)
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Crook's tube
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device that produces a glowing stream of electrons
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S-cloud
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ground state, spherical
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P-cloud
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excited state, hour glass shaped
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Chadwick
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discovered the neutron
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What part of an atom interacts in a chemical change?
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electron
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Electronic structure
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arrangement of electrons
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Electromagnetic radiation is...
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energy that travels through space in the form of electromagnetic waves
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Another name for electromagnetic radiation
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radiant energy
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Types of EM
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gamma, x-ray, UV, IR, visible, radio, microwaves
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measurable properties of waves
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speed, wavelength, and frequency
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Frequency
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number of waves that occur in a certain amount of time, unit = Hz
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Wavelength
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distance between identical points of successive waves, unit = m
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speed
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distance/time, unit = M/S
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Relationship between frequency and wavelength
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inversely proportional
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What does amount of energy depend on?
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temperature
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Planck's hypothesis
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Energy can be emitted or absorbed only in discrete amounts (in whole numbers of quanta)
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Quantized energy versus continuous energy
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stairs = specific, ramp = continuous
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quanta
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amounts of energy too small for us to notice
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Einstein
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photoelectric effect
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Photoelectric effect
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a phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency
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Photon
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particle of light
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How did Einstein explain the photoelectric effect?
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he suggested that a beam of light is really a stream of particles; if the photon has enough energy it can free an electron from the metal
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When can there be no photoelectric effect?
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if the wavelength is greater than the max wavelength and E is greater than min energy
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threshold frequency
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frequency required for electrons to be freed from the metal
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Difference between continuous and line spectrum
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Continuous: all wavelengths, line: specific wavelengths
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What happens when excited electron returns to ground state?
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gives off energy in the form of EM radiation
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Ground state
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N=1, lowest energy state of system
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Excited state
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N>1, energy state higher than ground state
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What color does Hydrogen gas emit when moving from excited to ground state?
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violet, blue, green, red
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Bohr
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theory and model of the hydrogen atom; adopted Planck's idea that energies assoc. with electrons must be quantized
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In absence of external electric and magnetic fields, cathode rays
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travel in a straight line from cathode to anode
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When there is a magnetic field applied to a cathode ray tube...
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rays curve at right angles to the magnetic field
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If a positively charged particle is directed between positively and negatively charged plates...
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it will bend towards the negatively charged plate
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What was discovered in the cathode ray tube experiment?
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1) that cathode rays consist of negatively charged particles, 2) the charge to mass ratio, 3) that they travel from cathode to anode
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Why did some oil drops have different charges?
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some drops had more electrons than others
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Charges on top and bottom plate
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top = positive, bottom = negative
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Gold Foil Experiment led to discovery of the...
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nucleus
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Most particles directed at the gold foil passed straight through. This led to the conclusion that...
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atoms are mostly empty space
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The backward deflection of alpha particles in the Gold Foil Experiment gave evidence of an atom's...
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nucleus
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A nuclear particle with about the same mass as a proton but no electrical charge is a...
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neutron
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Angles of deflected particles led to what conclusion?
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positive region at the center of the atom
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the nucleus is...
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1) very dense, 2) positive charge, 3) makes up most of mass of the atom
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