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Democritus
He believed that all matter consisted of extremely small particles could not be divided. He thought there were different types of atoms with specific properties. -
John Dalton
His atomic theory: 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. -
J.J. Thomson
He used a a device that had a sealed glass tube that had most of the air removed with a metal disk at the end of each tube . Wires connected the metal disks to a source of electricity . When it is turned on one disk becomes negitivley charged the other becomes positive. A glowing beam appears in the space between the disks . He hypothisized that the beam was a stream of electricly charged particles that interacted with the air in the tube and caused the air to glow. By doing this expeiriment he -
Hantaro Nagaoka
Two things That Led Him To His Model a very massive nucleus (in analogy to a very massive planet) electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces).That is why he called his model the Saturnian
Model -
Ernest Rutherford
Ernest Rutherford's expeirement was the gold foil expeiriment. He aimed a narrow beam of alpha particles at the gold with a screen around it made of material that produced a flash of light when struck with a fast moving alpha particle. He could figure out a path of the alpha particle as it passed through the gold. He discovered that the positive charge from the alpha particles is not evenly spread but concentrated in a very small area called a nucleus -
Niels Bohr
He discovered that electrons traveled in orbits around the atom's nucleus that the chemical properties of the element was largely determined by the number of electrons in the outer orbits that an electron could drop from a higher-energy orbit to a lower one, emitting a photon (light quantum) of discrete energy -
Werner Heisenberg & Erwin Schrodinger
The electron cloud model shows the probable locations of electron in an atom. The probability of finfing a n electron is higher in the denser regions of the cloud. -
James Chadwick
He proved neutrons. He concluded in his experiment that the particles produced were neutral because a charged object id not deflect their paths
