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Glencoe Chemistry Matter and Change - Chapter 4

Chemistry Matter and Change - Glencoe - Chapter 4
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Dalton's atomic theory
States that matter is composed of extremely small particles called atoms; all atoms of the same element are identical; atoms cannot be created, destroyed, or divided into smaller particles.
Democritus
Proposed that matter was not infinitely divisible, but instead made of tiny individual particles called atomos.
Thomson
Used the Cathode Ray tube to determine the charge-to-mass ratio of the electron; mass much less than that of the atom - meant atom was made of smaller particles; plum pudding model
Cathode Ray
proved the existence of negatively charged particles; constructed a glass tube with wires inserted in both ends, and pumped out as much of the air as they could, an electric charge passed across the tube from the wires would create a fluorescent glow
Rutherford
Gold foil experiment: (atom is mostly empty space, atoms contains a dense, positively charged nucleus); discovered protons.
Gold Foil Experiment
This was Ernst Rutherford's experiment that led to the discovery of the nucleus as the small, dense, positively charged center of the atom and the development of the nuclear theory of the atom.
Bohr Model
model of the atom in which electrons move rapidly around the nucleus in paths called orbits
Schrodinger
formulated a mathematical formula that describes probable area called orbitals where electrons are most likely located = quantum mechanical model in 1926
Heisenberg
If all particles are "waving," the it is impossile to know the object's velocity and position at the same time. To know one, we have to "stop" the other
Chadwick
discovered the neutron
Atom
Smallest particle of an element that retains all the properties of the element, electronically neutral, spherically shaped, and composed of electons, protons, and neutrons
Electron
Negatively charged, fast moving particle with an extremely small mass thta is found in all forms of matter and moves through the empty space surrounding an atom's nucleus
Nucleus
The extremely small, positively charged, dense center of an atom that contains positively charged protons and neutral neutrons
Proton
A subatomic particle in an atom's nucleus that has a positive charge of 1+
Neutron
A neutral, subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton
Atomic Number
The number of protons in an atom
Isotope
Atoms of the same element with different numbers of neutrons
Mass number
The number of an element's name, representing the sum of its protons and neutrons
Atomic Mass Unit (amu)
One-twelfth the mass of a carbon-12 atom
Atomic Mass
The weighted average mass of the isotopes of that element
Calculating weighted average atomic mass of an element
The sum of the mass contribution of each element

mass contribution = % abundance x mass of isotope
Why is an atom neutral?
Equal number of protons and electrons
Particles of atom with mass
protons and neutrons
Positive charged particle of atom
proton
Negatively charged particle of atom
electron
How to calculate mass number
add protons and neutrons
How to calculate # of neutrons
subtract number of protons from mass number
Which particle is equal to the atomic number
# of protons
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