Early Atomic Theory

Greeks

• in 300bc Democritus said atoms were invisible particles
• first mention of atoms (atomos)
• not a testable theory, only concept
• no mention of nucleus or sub atomic particles
• cannot explain chemical reactions
• this theory was the most accepted veiw for over 2000 years

Lavoisier (later 1700s)

• law of conservation of mass
• law of definite proportions
• wasn't a true atomic theory because it didnt discuss what atoms were or how they were arranged

Proust (1799)

• if a compound is broken down into its constituents, the products exist in the same ratio as the compound
• experimentally proved Lavoisier Laws

Dalton (early 1800s)

• atoms are solid, indestructable spheres (like billiard balls)
• provides for different elements
• no mention of subatomic particles
• cannot explain isotopes
• no mention of the nucleus

J.J. Thompson (1850s)

• raisin bun model
• solid positive spheres, with negative particles embedded in them
• first atomic theory to have positive and negative charges (protons and neutrons)
• introduces idea of nucleus
• no mention of neutrons so radioactive decay cannot be explained
• does not explain how electrons can exist outside nucleus
• does not explain neutrons role in chemical bonding

Rutherford (1950)

• showed that atoms have a positive centre with electrons outside it
• resulted in planetary models
• explains why electrons spin around the nucleus
• suggests atoms are mostly empty space
• should be unstable
• no mention of neutrons
• does not explain valence level electrons role in chemical bonds

i just had to put these guys in here cuz it is a prime example of how white kids can't rap and how i should never attempt it :P they mention dalton, thompson, rutherford and some other guy i dont know. ill explain Bohr after

Bohr (1920s)

• electrons must onlt exist in specific orbitals around nucleus
• explains how valence electrons are involved in bonding
• explains the difference between ionic and covalent bonding
• resolves the problem of atomic instability
• includes the neutron (discovered 1932)
• explains atomic emission spectra

oh look more white kids doing a terrible job of rapping! hahah at least they get his story across.

k so thats all we did today, a whole bunch of notes and learning about old folks who change chemistry as we know it!