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Atomic Theories and Electron Configuration

Terms in this set (13)

Democritus (460-370 BC)
-1st person to propose that matter is not infinitely divisible
-Known as atomos^^
-Matter is empty space through which atomos move
Aristotle (384-322 BC)
-Disagreed with the empty space idea
-Rejected Democritus's idea of atomic theory
-Believed all matter was fire, earth, air, and water
John Dalton (1766-1844 AD)
-All matter is made of atoms
-All atoms of a given element are identical and are different from atoms of to other elements
-Atoms cannot be created, destroyed, or divided into smaller particles
-Atoms combine in simple whole # ratios to make compounds
-In a chemical reaction, atoms are separated, combined, and arranged
J.J. Thomson (1856-1940 AD)
-Worked with the cathode ray tubes (CRT's)
-Deduced that the negatively charged particles flowing through the CRT were electrons....hence the first subatomic particle was discovered
-Proposed a model of an atom to explain the neutrality of an atom
-Plum Pudding Model
Ernest Rutherford (1871-1937 AD)
-Graduate student of J.J
-Inadvertently disproved the Plum Pudding Model
-fired alpha particles (positively charged) at gold foil
-Some alpha particles were deflected at huge angles
-Proposed that the atom had a tiny, dense central portion that is positively charged...called the nucleus
-Electrons move through empty space around the nucleus
-Later stated that protons were in the nucleus
James Chadwick (1891-1974 AD)
-Proposed that the nucleus had another particle in it with a mass near that of the proton but with no charge
Niels Bohr (1885-1962 AD)
-Proposed a quantum model of the atom in which the electrons followed distinct orbits around the nucleus
-it worked for Hydrogen (H)
Louis de Broglie (1892-1987 AD)
-Proposed that the electrons traveled in a wave-like orbit
-Known as the Quantum Mechanic Model
Valence Electrons
Electrons that live in the outer most energy level or farthest from the nucleus
-Aufbau Principle
-Pauli Exclusion Principle
-Hund's Rule
Electrons shall follow these three rules.
Aufbau Principle
-Comes from German word meaning "to build"
-Electrons will occupy lower energy orbitals first
Pauli's Exclusion Principle
-An atomic orbital can hold at most two electrons
-If an atomic orbital holds two electrons, they must have opposite spins
Hund's Rule
-When filling atomic orbitals of equal energy, place electrons with parallel spins in the orbitals first, then, place the oppositely spinning electrons into the orbitals
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