chem scientists

Democritus

Greek philosopher

Billiard Ball model

1st atomic model showing that atom is indestructible

robert boyle

first modern chemist
defined element as substance that cannot be broken down into 2 or more simpler substances chemically

Joseph Priestley

discovered oxygen in 1794

Antoine Lavoisier

law of conservation of mass--mass cannot be created or destroyed
father of modern chemistry

Joseph Proust

law of definite proportions in 1799--given compound always contains the same elements in the same proportions by mass

John Dalton

atomic theory of matter

atomic theory of matter

proved:
all matter has atoms
atoms of different elements combine in simple whole number ratios to form compounds
atoms can be combined

Benjamin Franklin

flew a kite and discovered 2 types of electrical charges

Michael Faraday

structure of atoms is related to electricity

J.J. Thomson

used cathode ray to see negatively charged particles
named electrons and determined ratio of electron's charge to its mass

plum pudding model

second atomic model made by Thomson
showed all particles in the same atom
atom is postivive charge with electrons embedded

Robert Millikan

oil drop experiment determined charge of single electron

Henri Becquerel

discovered radioactivity in 1896

Ernest Rutherford

gold foil experiment showed that atom is mostly empty space with a very tiny

Rutherford Model

3rd atomic model
electrons move around nucleus
mostly empty space

Niels Bohr

discovered model of hydrogen atom that linked atom's electron with photon emission

Planetary Model

electrons travel around nucleus in fixed orbits
propsed by Bohr

Henry Moseley

named proton
atomic number of atom defines identity of element (equal to protons)

James Chadwick

discovered neutrons
slightly heavier than protons

Max Planck

object emit energy in small amounts called quanta
relationship between a quantum of energy and frequency of radiation

Albert Einstein

said electromagnetic radiation has dual-wave particle nature
particles of light carry quantum of energy--photons

Louis de Broglie

electrons are confined to space around nucleus and can only exit at specific frequencies

Werner Heisenberg

uncertainity principle
impossible to determine simutaneously the position and velocity of electron or any other particle

Erwin Schrodinger

developed equation that treated electrons as waves
probability of finding electron at given place around nucleus
electrons don't travel in neat paths and exit in certain regions--orbitals

quantum theory

mathematically describes wave properties of electrons
heisenberg

quantum mechanical model

current atomic model
positive nucleus with fuzzy cloud of electrons