CJ's Atomic Theory History Timeline

Democritus

300

All matter conisted of really small particles that could notbe seperated. Called them atoms which in Greek was atomos which meant "uncut" or "indivisble". Democritus thought that they're were different types of atom with specific sets of properties. Also thought thatatms in liquids were smooth and in solids it was hard and prickly

Aristotle

400

Born in 384 BC Aristotle a Greek philosopher said there was a limit to the number of time matter could be divided.Aristotle had used the diagram to the left of earth,wind,water and fire as his experiment

John Dalton

Sep 6, 1803

Born in 1756 Spet. 6 was when he was born.1803 was when John Dalton made his theory. He was a teacher who mostly ran experiments because he was so interseted in weather. Dalton ran a experiment gathering evidence for the existence of atoms by measuring masses of elements that combinewhen compounds form. Dalton suggested that all matter is made up of individual particles for atoms, which cannot be divided. And each atoms is a tiny solid shpere with a different mass like the figure to the left.

JJ Thomson

Dec 18, 1856

Born in 1856 JJ Thomson used many electric currents to show for examples as atoms in many experiments. His experiment was using a sealed tune filled with gas at low pressure.Metal disks and a source of electric current for an experiment. His hypothesis was a stream of charged particles that interacted with the air in the tube and caused the air to glow. He did test his hypothesis and the plates cause the beam to deflect or bend from its straight path. His model is normal with no + or - charge.

Max Planck

Oct 31, 1900

In1900 Germany Idea/Experiment: A scientific philosopher Planck's Principle was that "A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it." How this contributed to our understanding of the atom: Planck, a German physicist, is considered the founder of the quantum theory.

Hantaro Nagaoka

Oct 31, 1904

Born in 1865 a japanese physicist suggests that an atom has a central nucleus. Electrons move in orbits like the rings around saturn.Nagaoka’s most notable work included the Saturnian model and his work on spectroscopy( spectroscopy-is the study of the interaction between matter and radiated energy).

Ernest Mardsen

Nov 1, 1909

Born in 1889 the English-New Zeland physicicst was know for heping Ernest Rutherford and his discovery of the new and improved atom. Using the Gold foil experiment. As one of Rutherford's students Rutherford asked one of his students being Mardsen to help him on this experiment and get research

Ernest Rutherford

Oct 31, 1911

Discovered that uranium emits fast-moving particles that have a positive charge. He used the gold foil experiment, but mostly that was done by John Mardsen, one of his students. In Rutherford's model all of an atom's positive charge is concentrated in its nucleus.

Neihl Bohr

Oct 31, 1913

Born in 1885 was a Danish Physicist from Denmark. Neihl Bohr's model of the atomic theory the electrons move spherical orbits at fixed distances from the nucleus.Fundamental contributions to the understanding of atomic structure and quantum mechanics.(quantum-The amount of energy regarded as a unit.)

Henry Mosely

Oct 31, 1914

In 1914 England Henry's Idea/Experiment: Studying under Ernest Rutherford, Moseley developed the application of X-ray spectra to study atomic structure. How this contributed to our understanding of the atom: By measuring the wavelengths of the x-rays given off by certain metals, Moseley was able to determine the number of positive charges in the nucleus of an atom. This was the first concept of the atomic number

Louis de Broglie

Oct 31, 1924

Frenchman Louis de Broglie born in 1892 proposed that moving particles like electrons have some properties of waves. de Broglie and his assistants did an experiment firing electrons at a crystalline nickel target.

Erwin Schrodinger

Oct 31, 1926

Born in 1887 Erwin developed mathematical equations to describe the motion of electrons in atoms. His model was developed into a electron cloud.

James Chadwick

Oct 31, 1932

Born in 1891 England physicist James confirms the existence of neutrons which have no charge Atomic nuclei contain neutrons and positively charged protons. As his experiment Chadwick smashed alpha particles into beryllium, a rare metallic element, and allowed the radiation that was released to hit another target: paraffin wax. When the beryllium radiation hit hydrogen atoms in the wax, the atoms were sent into a detecting chamber.