DemocritusDemocritusAbdera 460-370 B.C.Abdera 460-370 B.C.

He first attempted to create materialism.He first attempted to create materialism.Everything is composed of atomsEverything is composed of atoms

. .

Antione LavoisierAntione Lavoisier

17721772Total mass of a product of a chemical Total mass of a product of a chemical

reaction is always the same thing as the reaction is always the same thing as the total masstotal mass

Conservation of massConservation of mass

Law of Conservation of MassLaw of Conservation of Mass

17891789Matter can not disappear it can only be Matter can not disappear it can only be

rearrangedrearrangedAt high speeds mass changes to energyAt high speeds mass changes to energy

Joseph Louis ProustJoseph Louis Proust

17981798Created the law of constant compositionCreated the law of constant compositionConstant compositionConstant composition

Dalton’s Atomic TheoryDalton’s Atomic Theory

17991799Law of constant composition Law of constant composition Oxygen and Carbon combined make 2 Oxygen and Carbon combined make 2

compounds compounds

John DaltonJohn Dalton

18031803 Recorded the first Recorded the first

tables of relative tables of relative atomic massatomic mass

Atomic numberAtomic number

Law of Definite ProportionsLaw of Definite Proportions

18051805Law say if formula AB is constant then the Law say if formula AB is constant then the

weight ratio will stay the sameweight ratio will stay the sameWeight ratio stays the sameWeight ratio stays the same

Dmitri Mendeleev Dmitri Mendeleev

18691869Created the periodic tableCreated the periodic tableList of elementsList of elements

Eugene GoldsteinEugene Goldstein

18861886 Investigated X-raysInvestigated X-raysDiscovered cathode raysDiscovered cathode rays

Erwin SchrodingerErwin Schrodinger

1887-19611887-1961Created the Schrodinger Wave EquationCreated the Schrodinger Wave EquationUsed to describe behavior of electrons in Used to describe behavior of electrons in

atoms atoms

Cathode Ray TubeCathode Ray Tube

189318932 positive leads connected into a neon 2 positive leads connected into a neon

tube will make it light uptube will make it light upElectric makes light Electric makes light

J.J. ThompsonJ.J. Thompson

18971897 Discovered that Discovered that

cathode rays are cathode rays are small steams of small steams of atomsatoms

An electron has a An electron has a negative chargenegative charge

Plum Pudding Atomic ModelPlum Pudding Atomic Model

18971897 He said that there has He said that there has

to be a positive and to be a positive and negative charge to negative charge to balance out an atombalance out an atom

Atoms are neutral Atoms are neutral

Ernest RutherfordErnest Rutherford

18981898 Discovered and Discovered and

studied alpha studied alpha particles and particles and discovered the discovered the nucleusnucleus

NucleusNucleus

Marie CurieMarie Curie

19021902Discovered the radio active elementsDiscovered the radio active elementsRadio active elementsRadio active elements

Rutherford ModelRutherford Model

19091909 Model of a nucleus Model of a nucleus

and electronsand electrons Nucleus is in the Nucleus is in the

center and the center and the electrons orbit itelectrons orbit it

Robert MillikanRobert Millikan

19111911Made an oil drop experimentMade an oil drop experimentMade electron have an electric chargeMade electron have an electric charge

Bohr Planetary ModelBohr Planetary Model

19131913 He thought that He thought that

electrons only orbit in electrons only orbit in one directionone direction

They are called They are called stationary orbitsstationary orbits

Niels Bohr Niels Bohr

19131913 Considered the term Considered the term

of stationary orbits for of stationary orbits for the electrons and that the electrons and that there is more than there is more than one level of orbitone level of orbit

Electron cloudElectron cloud

Henry MosdeleyHenry Mosdeley

19131913Numbered the elementsNumbered the elementsOrder of elementsOrder of elements

Quantum Mechanical ModelQuantum Mechanical Model

Mathematical Mathematical equation developed equation developed by Schrodingerby Schrodinger

Calculated where Calculated where electrons are at any electrons are at any given momentgiven moment

Gold Foil ExperimentGold Foil Experiment

19201920 It showed that the It showed that the

nucleus is positive nucleus is positive and the electrons and the electrons orbit it orbit it

James ChadwickJames Chadwick

19321932Found the neutronFound the neutronHis discovery led to nuclear fission and the His discovery led to nuclear fission and the

atomic bombatomic bomb

Lise Meitner Lise Meitner

19661966First discovered nuclear fission First discovered nuclear fission