-
400
Democritus
Democritus
Date Lived
460-370 B.C.E
Discovery
400 B.C. -
400
Democritus
Democritus's Discovery
1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position, and arrangement.
->Solids are made of small, pointy atoms.
->Liquids are made of large, round atoms.
->Oils are made of very fine, small atoms that can easily slip past each other. -
John Dalton
John Dalton
Lived-Died
September 6, 1776- July 27,1884 -
John Daltons Discovery
Atomic Theory
Elements consisted of tiny particles called atoms
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.
Dalton's law of partial pressures states that the total pressure of a mixture of gases is the sum of the partial pressures of the various components. -
John Daltons form
Partial Pressure
PT = P1 + P2 + P3 + ... -
J.J Thomson
J.J. Thomson
1856-1940
Discovery
1884 -
J.J Thomson Discovery
Electrons
1 . Electrons travelled in a straight line.
2. Cathode rays especially the electrons have momentum and kinetic energy.
3. Electrons produce heat when they strike an object.
4. X-rays are emitted by the electrons.
5.When electric field and magnetic field are applied, the electrons deflect.
6. Electrons travel with high velocities.
7.Electrons produce fluorescence when they strike crystals, minerals and salts. -
Ernest Rutherford
Ernest Rutherford
1871-1937
Discovered Radioactive Gas in 1889 -
Ernest Rutherford
In 1889 he discovered a radioactive gas called Radon today.
He discovered rays from radioactive materials, which he named Alpha and Beta -
Ernest Rutherford
He discovered the nucleus in 1911 using the gold foil experiment. -
Robert Milliken
Robert Milliken
Lived-Died
1863-1953
Discovery
1913 Measurement of an electronic charge -
Robert Millikan
Measured a charge on an electron
1. The Millikan Oil Drop Experiment. An experiment performed by Robert Millikan in 1909 determined the size of the charge on an electron. He also determined that there was a smallest 'unit' charge, or that charge is 'quantized'.
2. Measured a charge on the electron -
Oil Drop
Oil drop experiment
The atomizer from a perfume bottle was used to spray water or oil droplets into a sample chamber. Some of these droplets fell through a pinhole between two plates of an electric field, where they could be observed through a microscope. -
Niels Bohr
- The electron in a hydrogen atom travels around the nucleus in a circular orbit.
- The energy of the electron in an orbit is proportional to its distance from the nucleus. The further the electron is from the nucleus, the more energy it has.
- Only a limited number of orbits with certain energies are allowed. In other words, the orbits are quantized.
- The electron in a hydrogen atom travels around the nucleus in a circular orbit.
-
Niels Bohr
- The only orbits that are allowed are those for which the angular momentum of the electron is an integral multiple of Planck's constant divided by 2.
- Light is absorbed when an electron jumps to a higher energy orbit and emitted when an electron falls into a lower energy orbit.
- The energy of the light emitted or absorbed is exactly equal to the difference between the energies of the orbits.
-
Ernest Rutherford
He discovers protons in the year 1918. He changed Nitrogen to Oxygen; he split the atoms.Discovered the Proton in 1918 -
James Chadwick
1) He discovered the particle in the nucleus of an atom that became known as the neutron because it has no electric charge
2)Chadwick became professor of physics at Liverpool University in 1935. As a result of the Frisch-Peierls memorandum in 1940 on the feasibility of an atomic bomb -
Niels Bohr
Lived- Died
1885-1962
Discovery
1912-1913 -
James Chadwick
1881-1974
Discovery 1932
on neutron
