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| easily explained conservation of mass in a reaction as the result of the combination, separation, or rearrangement of atoms |
Dalton's atomic theory |
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| revived the idea of the atom in the early 1800s based on numerous chemical reactions |
John Dalton |
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| disagreed with Democritus because he did not believe empty space could exist |
Aristotle |
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| first person to propose the idea that matter was not infinitely divisible, but made up of individual particles called atomos |
Democritus |
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| many believed matter could be? |
endlessly divided into smaller and smaller pieces |
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| many ancient scholars believed matter was composed of such things as? |
earth, water, air, and fire |
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| chemical behavior can be explained by considering only an atom's what? |
electrons |
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| scientists have determined that protons and neutrons are composed of subatomic particles called what? |
quarks |
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| all atoms are made of these three fundamental subatomic particles |
electron, proton, and neutron |
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| received the Nobel Prize in 1935 for discovering the existence of neutrons, neutral particles in the nucleus which accounts for the remainder of an atom's mass |
James Chadwick |
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| the repulsive force between what two things caused deflections? |
positively charged nucleus and positive alpha particles |
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| held within the atom by their attraction to the positively charged nucleus |
electrons |
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| concluded that atoms are mostly empty space |
Ernest Rutherford |
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| by aiming the particles at a thin sheet of gold foil, he expected that paths of the alpha particles to be only slightly altered by a collision with an electron |
Ernest Rutherford |
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| studied how positively charged alpha particles interacted with solid matter |
Ernest Rutherford |
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smiley Tue, 24 Nov 2009 04:50:09 GMT |
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| this scientist's plum pudding model of the atom states that the atom is a uniform, positively charged sphere containing electrons |
J.J. Thomson |
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| with the electron's charge and charge-to-mass ratio known, he calculated the mass of a single electron |
Robert Millikan |
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| used the oil-drop apparatus to determine the charge of an electron |
Robert Millikan |
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| measured the effects of both magnetic and electric fields on the cathode ray to determine the charge-to-mass ratio of a charged particle, then compared it to known values |
J.J. Thomson |
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| a stream of particles carrying a negative charge |
cathode rays |
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| an instrument that allows individual atoms to be seen |
scanning tunneling microscope (STM) |
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| high energy radiation that has no electrical charge and no mass, is not deflected by electric or magnetic fields, usually accompanies alpha and beta radiation, and accounts for most of the energy lost during radioactive decay |
gamma ray |
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| a high-speed electron with a 1- charge that is emitted during radioactive decay |
beta particle |
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| radiation that is made up of beta particles; is deflected toward a positively charged plate when radiation from a radioactive source is directed between two electrically charged plates |
beta radiation |
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| a type of equation that shows the atomic number and mass number of the particles involved |
nuclear equation |
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| a particle with two protons and two neutrons, with a 2+ charge; is equivalent to a helium -4 nucleus, can be represented by (fish sign); and is emitted during radioactive decay |
alpha particle |
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smiley Tue, 24 Nov 2009 04:50:09 GMT |
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| radiation that is made up of alpha particles; is deflected toward a negatively charged plate when radiation from a radioactive source is directed between two electrically charged plates |
alpha radiation |
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| a spontaneous process in which unstable nuclei lose energy by emitting radiation |
radioactive decay |
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| a reaction that involves a change in the nucleus of an atom |
nuclear reaction |
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| the rays and particles - alpha and beta particles and gamma rays - that are emitted by radioactive materials |
radiation |
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| the process in which some substances spontaneously emit radiation |
radioactivity |
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| the weighted average mass of the isotopes of that element |
atomic mass |
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| one-twelfth the mass of a carbon-12 atom |
atomic mass unit (amu) |
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| the number after an element's name, representing the sum of its protons and neutrons |
mass number |
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| atoms of the same element with different numbers of neutrons |
isotope |
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| the number of protons in an atom |
atomic number |
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| a neutral, subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton |
neutron |
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smiley Tue, 24 Nov 2009 04:50:09 GMT |
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| a subatomic particle in an atom's nucleus that has a positive charge of 1+ |
proton |
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| the extremely small, positively charged, dense center of an atom that contains positively charged protons and neutral neutrons |
nucleus |
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smiley Tue, 24 Nov 2009 04:50:09 GMT |
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| a negatively charged, fast-moving particle with an extremely small mass that is found in all forms of matter and moves through the empty space surrounding an atom's nucleus |
electron |
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| radiation that originates from the cathode and travels to the anode of a cathode-ray tube |
cathode ray |
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smiley Tue, 24 Nov 2009 04:50:09 GMT |
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| the smallest particle of an element that retains all the properties of that element; is electrically neutral, spherically shaped, and composed of electrons, protons, and neutrons |
atom |
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smiley Tue, 24 Nov 2009 04:50:09 GMT |
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| states that matter is composed of extremely small particles called atoms; atoms are invisible and indestructable; atoms of a given element are identical in size, mass, and chemical properties; atoms of a specific element are different from those of another element; different atoms combine in simple whole-number ratios to form compounds in a chemical reaction, atoms are separated, combined, or rearranged |
Dalton's atomic theory |
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