Development of Atomic Theory

Democritus

first atomic theory - no experimentation

Lavoisier

Law of Conservation of Mass

Proust

Law of Definite Composition

Dalton

billiard ball model

Crookes

discovers cathode rays

Thomson

measured charge-to-mass ratio of the electron

electrons are part of all matter

Millikan

"oil drop" experiment electrons have a specific charge

Rutherford

"gold foil" experiment (3 observations and 2 conclusions)

Bohr

hydrogen line spectra

Chadwick

discovered the neutron

Dalton

first modern atomic theory (5 statements)

Thomson

"discoverer of the electron"

Thomson

"Plum pudding" model of the atom

Millikan

measured the charge of the electron

Bohr

"solar system" atom

energy levels

Arrhenius

atoms form ions

Faraday

atoms lose or gain specific numbers of electrons, electricity is the glue that holds chemicals together

Rutherford Thomson and associates

proton

Francis Aston

mass spectrometer

Soddy

Isotopes of an element - same proton, different neutron

Brookes

Elements turn into other elements when emitting radiation

Max Planck

energy coming from light is quantized

quantum

a discrete amount of energy - ex. photon

Einstein

explained photoelectric effect

blackbody radiation

an experiment involving the analysis of light produced by a heated object

Kirchhoff

emission spectra and blackbody radiation

Hertz

discovered the photoelectric effect

Balmer

math formula describing the line spectra of hydrogen

kirchhoff and bunsen

emission spectra and absorption spectra

Mendeleev

Patterns in the periodic table

Bohr - quantum number

principle quantum number - n

Sommerfeld

secondary quantum number - l

Zeeman Effect

magnetic quantum number - ml

Wolfgang Pauli

spin quantum number - ms

Pauli Exclusion priciple

no two electrons can have the same four quantum numbers

aufbau principle

electrons are added to the lowest energy level first

Hund's Rule

each orbital at the same energy level gets one electron each before being paired up

Louis de Broglie

electrons can act like waves

Schrodinger

electrons are standing waves - formula - wave function of an electron

Heisenberg

Uncertainty principle - both the position and movement of electrons can't be predicted at the same time

Orbital

defined region of space where there is a probability of finding the electron