Atomic Theory

John Dalton 1810-1811

Mar 10, 1810

(dont worry about dates)
John Dalton is considered the father of the Modern Atomic theory
with his 5 main points of Atomic Theory
1Elements are made of extremely small particles called atoms.
2Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3Atoms cannot be subdivided, created, or destroyed.
4Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

John Dalton 1810-1811 part 2

Mar 10, 1810

5 In chemical reactions, atoms are combined, separated, or rearranged. Dalton also proposed the rule of simplicity which created contraversy as it could not be independantly confirmed.

Amedeo Avogadro 1811

Mar 10, 1811

In honor of Avogadro's contributions to molecular theory, the number of molecules in one mole was named Avogadro's number, NA or "Avogadro's constant". It is approximately 6.0221415 × 1023. Avogadro's number is used to compute the results of chemical reactions. It allows chemists to determine amounts of substances produced in a given reaction to a great degree of accuracy.

J.J. Thomson 1897

Mar 10, 1897

J.J. Thomson is credited to the discovery of the electron in 1897
other scientest had suggested that atoms had been made up of a more fundamental unit (hydrogen) until J.J. Thomson has suggested that they were 1,000 times smaller than the atoms and called them electrons

Ernest Rutherford

Mar 10, 1911

Tested to find what an atom really is through bombaring gold foil with alpha particles and found that most alpha particles went through but some were deflected through this Ernest Rutherford found out that atoms are mostly made up of empty space

Robert Millikan

Mar 10, 1911

Performed an experiement (Oil Drop experiment) to find the charge of an electron. This allowed for the actual charge and mass values to be found (only one as it only needed one to work out the other) Millikan and his then graduate student Harvey Fletcher used the oil-drop experiment to measure the charge of the electron.

Niels Bohr

Mar 10, 1913

Niels Bohr improved the atomic model with the question of "why aren't electrons pulled into the nucleus?" he found that
1 Electrons travel in definite energy levels without radiating energy 2 Electrons in each orbit (of an atom) have a certain amount of energy 3 Energy increases as distance away from nucleus increases and 4 Electrons lose energy by dropping energy levels only if they receive or lose energy.