Period: 370 to 400
Democritus-Lived from 400 BC to 370 BC
-A Greek philophoser that proposed that matter was made up of small, hard, indivisble, particles, which he called atoms
- Had no evidence to support his theory
-Then modern atomic theory began in the late 1700s
John Dalton-Matter is composed of tiny indivisible particles called atoms.
-All atoms of the one element are identical but are not to other elements.
-Was born in cumbria but later died in manchester.
Joseph J. Thomson-Plum pudding model of the divisible atom
-atoms consist of uniform positve charge with also negatively charged particls.
-positive charge of sphere = the negatively charged
-Born in manchester but then died in cambridge
Robert Milikan-Born in morrison, illinios, then died in san marino california.
-Measured charges of electrons using a perfume bottle while there was water inside of it.
Enest Rutherford-Born in Brightwater, New Zealand. Then died in cambridge
-Proposed the model of the atom. Contains
-positively charged protons
-number of protons equal the number of electrons
Niels Bohr-Proposed planetary model for the hydrogen atom
-electrons move around the nucleus in a fixed orbit
-An electron can absorb energy and move to a higher energy orbit.
-Born in copenhagen, then died in denmark
- The nucleus of an atom contains neutrons, electrically neutral particles with a mass similiar of the protons it has. -Born and grew up in Bollington, united kingdom, then died in cambridge