THE ATOMIC THEORY

DEMOCRITUS

• was one of the first to state that atoms exist
• Greek philosopher
• stated that atoms were indivisible and indestructable

JOHN DALTON

• Created an atomic theory that states:
• all thing are made up of small, indivisible atoms
• atoms from the same element are identical
• atoms from different elements can be combined to create compounds
• when atoms are seperated, they create a chemical reaction

J.J. THOMSON

• discovered the electron
• created the cathode ray to test ifelectrons exist
• he also experimented with putting the elecron's charge to its mass
• the experiment helped him conclude that electrons are in all atoms

ROBERT A. MILIKAN

• experimented to find the quantity of an electrons charge
• concluded that an electron's mass is 1/1840 the mass of a hydrogen atom

EUGEN GOLDSTEIN

• as observing a cathode ray as he noticed particles flowing the opposite way
• concluded that the charge of the particles were positive which, later were called protons

ERNEST RUTHERFORD

• conducted the gold foil experiment to test Thomson's Plum Pudding model
• based on his experiment, he created a new atomic theory
• suggested that there was a core in the atom and named it the nucleus
• concluded that in an atom, the protons and neutrons are in the center
• also concluded that the electrons float around

NIELS BOHR

• suggested that the electrons in an atom are in an orbit around the nucleus
• created a model that included energy levels that the electrons were on

EDWIN SCHRÖDINGER

• created the quantum mechanical model
• used a math equation describing the behavior of an electron in a H atom
• the model states that the electrons move around the nucleus like a windmill
• his equation also led to a math expression called atomic orbital
• An atomic orbital is depicted as an area of space where an electron can be found

JAMES CHADWICK

• discovered a new subatomic particle: the neutron