-
400
Democritus
400 B.C. Democritus’ atomic theory said that all matter is made up small indestructible units he called atoms. -
Antoine Lavoisier
Lavoisier discovered the Law of Conservation of Mass. -
Law of Conservation of Mass
The Law of Conservation of Mass is that mass is not created or destroyed it is simply rearranged. -
John Dalton
John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together. -
Dalton's Atomic Theory
States that 1. All matter is made of atoms. Atoms are indivisible and indestructible. 2.All atoms of a given element are identical in mass and properties 3. Compounds are formed by a combination of two or more different kinds of atoms. 4. A chemical reaction is a rearrangement of atoms. -
Dmitri Mendeleev
Came up with a periodic table of the elements similar to the one used today. -
J.J. Thomson
J.J. Thomson determined the charge to mass ratio of electrons. -
Cathode Ray Tube
When electrons are put through a cathode tube they emit light. This led to the invention of TV's. -
Ernest Rutherford
Rutherford discovered alpha, beta, and gamma rays in radiation. -
Plum Pudding Model
Basically the pudding is positively charged and the plums dotting throughout are the negatively charged electrons. -
Robert Millikan
Discovered a way to weigh a electon. -
Rutherford Model
The mass of an atom is not spread all equally throughout the atom it is densly packed into the nucleas or middle. -
Gold Foil Experiment
The atom is mostly empty space and all the mass is in the nuclues. So when Rutherford shot a golf foil with gamma rays some shot back some just went straight through. -
Henry Moseley
Discovered that the elements should be catogorized by atomic number not atomic weight. Also that the number of protons in an element determines its atomic number. -
Bohr Planetary Model
The electrons orbit the nucleus in a set size and energy. Which we know thie is not true. -
Niels Bohr
Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit. -
Erwin Schrodinger
He determined Bohr’s planetary model was not correct. He determined that electrons could be within the energy levels and that their energy predicted where they were likely to be found he said it was impossible to predict exactly where an electron is located in any moment of time. He made a model called the electron cloud model. -
Quantum Mechanical Model
This is one of the model we use more frequently today. It uses electron cloud or orbits where they are suspected to be. It just shows a different way of looking at it -
Electron Cloud Model
This is that the electrons are not in one exact position in time. This is because of the fact that they are ocnstantly moving very fast. So there is a "cloud" that they can approxiamately be in or near. -
James Chadwick
James Chadwick discovered neutrons, particles whose mass was close to that of a proton.
