Key Discoveries and Theories in Atomic and Quantum Physics

Democritus

Proposed that matter is made of indivisible particles called atoms

John Dalton

Made the modern atomic theory; atoms of the same element are identical

J.J. Thomson

Discovered the electron using the cathode ray tube experiment

Ernest Rutherford

Discovered the nucleus through the gold foil experiment

James Chadwick

Discovered the neutron

Max Planck

Discovered that energy is quantized into discrete packets

Albert Einstein

Explained the photoelectric effect and that light has  particle like properties

Niels Bohr

Proposed electrons exist in fixed energy levels

Louis de Broglie

Wave Particle Duality: Proposed that all matter have wave and particle like properties

Werner Heisenberg

Made the uncertainty principle that you cannot know exact position and momentum at the same time of a particle

Erwin Schrödinger

Developed the wave equation describing electron orbitals

Dmitri Mendeleev

made the periodic table

Henry Moseley

Reorganized the periodic table by atomic number

Ionic Bonds

Electrostatic attraction between ions

Covalent Bonds

Sharing of electrons

Metallic

Free electron hold metal atoms together

Octet Rule

atoms bond in ways that give them eight electrons in their outermost layer

Electronegativity

the ability of an atom in a molecule to attract electrons to itself.

Bond Polarity

a measure of how electrons in a covalent bond are shared.

Dipoles

When two equal but opposite charges are separated by a distance,