-
340
Democritus
Around 340BC
•Proposed that everything is made up of tiny little particles called atoms that are generally indivisable.
Problems: Thought that they are inert, and like the things they made up -
-
John Dalton
•Date of Discovery: 1803
•Contributions: John Dalton proposed the theory “All matter is made up of small invisible particles termed atoms. Atoms of a given element possess unique characteristics and weight, and three types of atoms exist; simple, compound, and complex.
•How: As he was trying to combine gases, he discovered that he couldn’t with the ones that weren’t similar in elemental properties and wanted to know why.
•Problems?: He said that they could not be divided any smaller. -
Sources For Dalton
http://en.wikipedia.org/wiki/John_Dalton#Atomic_theory http://www.sciences360.com/index.php/how-john-dalton-came-up-with-the-atomic-theory-of-matter-25559/ http://dl.clackamas.cc.or.us/ch104-04/dalton's.htm http://www.universetoday.com/38169/john-daltons-atomic-model/ http://www.biography.com/imported/images/Biography/Images/Profiles/D/John-Dalton-9265201-1-402.jpg -
JJ Thomson
1897
•Discovered the electron, suggesting that an atom is made up of even smaller things.
•How: Discovered this during his explorations with Cathode Rays.
Problems?: Said that the electrons were stationed and not moving. -
-
Marie Curie
•Proved that atoms were not indivisable.
How: Working with radioactivity
Problems: Radiactivity was very dangerous, they did not elaborate on an atom. http://nikkibeecalanas.blogspot.com/2012/08/marie-curie-and-atomic-theory_17.html
http://upload.wikimedia.org/wikipedia/commons/d/d9/Mariecurie.jpg
http://upload.wikimedia.org/wikipedia/commons/d/d9/Mariecurie.jpg -
Ernest Rutherford
1909
•Rutherford revealed the nature of an atom's nucleus; a very smal, charged nucleus is orbited by electrons.
How: Used a gold foil expirement to project atoms through, but some bounced.
Problems: No protons were discovered. Plus the atom was very unstable. -
-
Niels Bohr
1913
•Bohr found that Rutherford's model was very unstable so he proposed that electrons absorb or emit eloctro-magnetic energy, can jump from atom to atom, and they orbit at a certaqin distance from nucleus.
How: There were problems with Rutherford that needed to be solved.
Problems: Multi electron atoms are not predicted by his model. -
-
Electron Cloud Model
•Developed by Erwin Schrödinger and Werner Heisenberg.
• The electron cloud model says we can not know exactly where an electron is, but the electrons are more likely to be in specific areas of an atom.
Problems: Still dont know exactly where particles are in an atom. -
-
Werner Heisenberg
•Created first version of quantum mechanics, said that electrons do NOT travel in neat orbits. He also calculated the behavior of electrons. -
-
James Chadwick
1932
•Discovered neutrons.
How: Expirementing with radiation showed that there were uncharged particles in the nucleus.
Problems: Did not pursue much further into an atom. -
-
Aristotle
•Believed that if you kept cutting matter in half, you would always have a smaller piece of matter.
He also believed in the four elements- Fire, Air, Earth, and Water.
384-322 BC http://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htm http://mrsvesseymathematicians.wikispaces.com/file/view/aristotle_stone.jpg/122672537/aristotle_stone.jpg
