Chem Unit 3 Scientists First scientists

Democritus - Atomos is the smallest unit, indivisible.

Aristotle - earth wind and fire made up atoms, believed Democritus was wrong and he was supported

Dalton - Atoms make up all matter and are indivisible, all atoms of element are identical (no isotopes or ions)

Crookes - made cathode ray tube

Thomson - discovered electron in crd, plum pudding model. Nobel prize in 1906

Millikan - discovered mass and charge of electron, oil drop apparatus

Rutherford - discovered protons, gold foil and alpha particles pass through, believed atoms were mostly empty space, discovered nucleus. concluded nucleus had protons

Chadwick - discovered neutrons. nobel prize in 1935

Moseley - discovered atomic number (unique protons), died in war young

Second Scientists

Planck - matter gains + loses nrg in small specific amounts (quanta). E=hv (energy=plancks constant x frequency)

Einstein - discovered photons (massless quanta carriers) nobel prize in 1921

Bohr- proposed quantum model for hydrogen atom. proposed ground state and + excited state (ground -> excited (when quantized) excited -> lower state (emits energy in the form of color)) electron moves around in certain circular orbits. each orbit got a quantum number (n)

De Broglie - predicted all moving particles have wave characteristics. his eq - lambda = h/mv (wavelength = plancks/mass x frequency)

**alternate equation - lambda=c/v (wavelength=speed of light/frequency)**

Heisenberg - uncertainty principle, can’t know velocity + position of particle at the same time. proved bohr wrong

Schrödinger - created (too complex) wave equation with hydrogen atoms electrons. quantum mechanical model of the atom

Pauli - exclusion principle, only 2 electrons per orbital, with opposite spins

Lewis - made electron dot structure containing valence electrons