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23 Cards in this Set
- Front
- Back
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4 element theory 400BC |
People who followed Aristotle believed all matter was a combination of: Air, Earth, Fire, and Water |
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Democritus 460-370 BC |
World is made up of empty space and tiny particles called atoms. (Didn’t believe 4 element theory) |
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Law of Conservation of Mass |
Lavoisier concludes matter is neither created nor destroyed, only changed. |
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The Law of Definite Proportion |
A compound contains exactly the same elements in exactly the same proportions by mass regardless of the size. |
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The Law of Multiple Proportions |
Atoms of 2+ elements may combine in different ratios to produce more than one compound. |
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J. J. Thomson 1897 |
Discovered the electron |
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J. J Thomson 1897 |
Atoms contain negatively charged particles from conducting the cathode ray experiment. Atoms must also have a positive change since atoms are know to be neutral. |
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Robert Millikan 1909 |
An American physicist who determined the charge of an electron via the oil drop experiment. |
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Ernest Rutherford 1909 |
Gold foil experiment: directed alpha particles at a thin sheet of gold foil and observed the path of deflection of the particles. |
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Ernest Rutherford 1911 |
Concluded that atoms have a dense, positively charged core (nucleus) which is surrounded mainly by “empty” space where electrons are found |
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Thomson’s model vs. Rutherford’s model |
Thomson’s model didn’t have a distinct positively charged nucleus, only positive charge Thomson’s model didn’t have an atom with mostly empty space |
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Niels Bohr 1913 |
Planetary model of the atom Proposed that electrons could move around in the nucleus only in certain allowed circular orbits. |
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Quantum Mechanical Model 1935ish |
Used today Electrons have particles and waves. Shows probable location of an electron Probability distribution: more dots=areas with higher prob. of finding an electron |
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Sir James Chadwick 1932 |
Discovered NUETRONS: a particle with the same mass as protons but with no electrical charge in the nucleus |
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S sublevel shape |
Sphere |
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P sublevel shape |
Dumbell |
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D and F sublevel shape |
Very complicated |
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Orbital |
Region of space around the nucleus where there is a high probability of finding an electron. |
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Aufbau Principle |
Electrons are added one at a time to the lowest energy orbitals first |
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Pauli Exclusion Principle |
There’s a maximum of 2 electrons per orbital and they must have opposite spins. |
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Hund’s Principle |
Electrons don’t pair up until they are forced to. |
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Degenerate orbitals |
Orbitals of equal energy (2px, 2py, 2pz) |
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Heisenberg Uncertainty Principle |
It is impossible to determine both the position and momentum of a particle simultaneously |
