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300
Aristotle's Theory
Mid 300s B.C.E Aristotle strongly disagreed with Democritus.
His theorey used great generalization
It stated that there were 4 elements: earth, fire, air, water with 4 quantities: warm, dry, cool, moist'
It was used for about 2000 years while the Democritus Model was put aside -
Period: 300 to
Atomic Theory
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400
Basic Atomic Theory
5th Century B.C.E Democritus said all things were composed of extremely small things called "atomos"
He stated nothing exists except atoms and empty space.
This is the first atomic theory known to man -
Modern Atomic Theory
John Dalton announced his theory 1) All elements consist of minuscule particles called atoms.
2) All atoms in an element are identical to each other.
3) All atoms in an element are different than those of other elements.
4) Atoms of one element combine with other elements to create compounds. They always combine in equal amounts.
5) Atoms cannot be created, divided, or destroyed. -
The Electron
JJ Thompson disxcovers the electron
He comes up wityh the Plum Pudding model -
Quantam Theory
Max Planck introduced the quantam theory
Atoms can emit quanta -
Rutherford
Performed the gold foil expirement
the atom is mostly empty space with a small positively charged nucleus containing most of the mass and low mass negatively charged particles orbiting this nucleus.
Predicted the nuetron -
Oil Drop Expirement
It was used to find the charge of an electron
It was completed by Robert Millikan and JJ Thompson -
Bohr's Model
Niels Bhor introduced his representation of the atom
His model is known as the planetary model.
Stated that the electrons moved around the nucleus in large orbits
Stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states. -
Louis de Broglie
introduced his theory of particle-wave duality
stated particles can behave like waves, and waves (radiation) can behave like particles
was fundamental for quatam mechanical model
Inspired Schrodinger -
Dual Nature of Light
The wave equation was confirmed mathematically by Erwin Schrodinger.
The equation helped determine probability location of electrons in an atom -
Uncertainty Principle
Werner Heisenberg stated that it's impossible to determine locaton and momentum of electrons simultaneously.
That is why they are described in orbitals instead of orbits
"cloud model aka quantam mechanical model" -
The Neutron
Although Rutherford predicted it, the neutron wasn't discovered until 1932 by James Chadwick.
Chadwick used scattering data to calculate the mass of this neutral particle
