Famous Chemists

Parmenides

500

Parmenides- 580-540 BC belived everything that already existed was made up of building blocks (his idea of the atom). He gave ideas to Demicritus.

Democritus

Sep 20, 600

Democritus- 400 BC He thought everything was made of atoms.

Aristotle

Sep 20, 700

Aristotle- 384-322 BC His ideas were not contested (no one argued his theory because he was thought to be a genius). He believed all matter was either fire, water, earth, or air. People believed him because he tutored very smart and important people.

Dalton

Sep 20, 1800

Dalton- 1800 an element is composed of one type of atom and a compound is a chemical combination of different kinds of atoms. Billiard ball model – Dalton's atomic theory 1. all elements are composed of tiny indivisible particles called atoms (false; atoms are divided by nuclear reactions) 2. atoms of the same elements are identical, atoms of one element are differnet from those of any other element (false; neutrons and electrons vary in the elements)

Dalton (continued)

Sep 20, 1800

1. atoms of different elements can physically mix or chemically combine to form compounds 4. atoms are rearranged in chemical reactions. Not destroyed or created or changed.

Mendeleev

Sep 20, 1871

Dimitri Mendeleev- 1871 first periodic table, sorted by weights(atomic mass), left gaps for other elements that were later added.

JJ (continued)

Sep 20, 1897

He compared the atom to plum pudding(positively charged goop) and electrons were random throughout like the plums. First model that showed anything but just a sphere. This wasn't widely accepted because there wasn't much proof besides the one experiment, but everyone agreed it was more advanced than it had been.

JJ Thomson

Sep 20, 1897

JJ Thomson- 1897 discoverd the electron, there were ideas of subatomic particles, but he caused a rush to learn more about subatomic particles and their purpose – cathode ray tube put gas in tube, ends connected to wire and ran elctricity through tube. he knew that if there were electrons in the tube they would line up and complete the circuit. This proved Dalton's model was wrong because it wasn't just a sphere. It was made up of other little parts.

Millikan

Sep 20, 1908

Millikan- 1908 carried out experiments to find quantity of charge(-1) and mass of electron(1/2000ths of an atom) and the mass of atom. He used the plum pudding model.

Rutherford

Sep 20, 1911

Rutherford- 1911 came up with the idea of a positive(protons) nucleus with negative electrons around the nucleus. He found the nucleus was very tiny and very dense. Rutherford's experiment- gold foil experiment – shot alpha particles at gold foil and according to the norm at that time they shouldve went straight through but some bounced off showning that there was a nucleus and the rest was mostly empty space.

Rutherford (continued)

Sep 20, 1911

Rutherford was a colleague with JJ and this experiment was intended to prove the plum pudding model because electrons were too small to deflect the particles they shouldve gone straight through but he found out that the nucleus deflected them.

Bohr

Sep 20, 1913

Bohr- 1913 electrons orbitted in rings(energy levels) and could jump from orbit to orbit and release energy.

Shroedinger

Sep 20, 1930

Cloud Model- Shroedinger- electrons are not necessarily in neat rings but in different shaped clouds depending on energy.

Chadwick

Sep 20, 1932

Chadwick- 1932 worked with Rutherford and discovered the neutron and its location in the nucleus (masses weren't making sense so they knew something was missing) same model as bohr's but with neutrons

Manhattan Project

Sep 20, 1941

Manhattan project- 1941 nuclear research, created atomic bomb for WW2. Seperated the atom and released energy. (Dalton's indivisbile theory was wrong.)