J.Coraccio+Time+Line+Project

//JULIANNA'S SUPER RIDICULOUSLY SWEET TIME LINE//

World Events

Leucippus (Greece) around 475 BC
 * Ancient.**

Leucippus came up with the idea of the atom before anyone else. He correctly thought an atom was an indivisible unit of matter. Proving empty space with awareness is also something he did first.



Democritus (Greece) 470 - 370 BC

Democritus is known as the co-originator of the atom. He thought that all matter is made up of various imperishable, indivisible elements.

Aristotle (Greece) 384 - 322 BC

Aristotle believed that different gods represented water, fire, air, earth. Each stood for a different season, which would later be called elements.




 * 466 - 1700.**

Galileo Galilei (Italy) 1564 - 1642

Galileo thought that an atom was indivisible and had no shape nor dimensions. He also believed that the world was composed of a infinite amount of atoms which were separated by a quantitatively infinite vacuum.

Evangelist Torricelli He proved the existence of the vacuum by studying problems connected with pumping water and by doing experiments, which he replaced water with mercury.

  






 * 1701 - 1800.**

Daniel Bernoulli (Dutch) 1700 - 1782

He assumed that the pressure of a gas consists of atoms crashing into the walls of the container filled with the gas. It was the first time when the atom was used in quantitatively and experimentally verifiable calculations.





(Yugoslavia) 1711 - 1787 He loved geometry. And even though he know Newton's work, he didn't accept the law of universal gravity 100%. He thought it might not be the rule in atomic scale. He thought that the existence of a field of force could be described using geometry. He said that atoms were particles without dimensions, they were reduced to geometric points.


 * 1801 - 1875**.

John Dalton (England) 1766 - 1844

Dalton came up with these four theories in 1832: 1. All matter is made of atoms: indivisible and indestructible. (which was false) 2. All atoms of a given element are identical in mass and properties. (which was correctomundo) 3. Compounds are formed by a combination of two or more different kinds of atoms. (which was true) 4. A chemical reaction is a rearrangement of atoms. (which was correct)



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Dymitrij Medelejev (Russia) 1834-1907//

He write a handbook for students. In doing so, he noticed similarities in every eight elements. He made the first periodic table of elements by putting all of the elements into columns. He left gaps for unknown elements.

(France) 1867 - 1934
 * 1876 - 1900**.

Marie investigated radioactivity, mainly. She removed uranium from the ore. With this information, she thought that inside the ore were new elements, also highly radioactive. In 1898, she and her husband discovered Polonium and Radium. Marie Curie received the Nobel in chemistry for her discoveries.

Wilhelm Conrad Röntgen (Germany) 1845 - 1943

He was the first scientist to observe and record X-rays in 1895. He was messing around with cathode ray instruments and found a flickering image cast by his instruments separated from them by some distance. He knew what he saw was not being cast by the cathode rays (or beams of electrons) because they could not go through air for any significant distance. After investigation, he named the new rays "X" because they were unknown.


 * Erwin Schrödinger** (Italy) 1877 - 1961

Schrödinger believed that atoms structures should be ascertained by a eigenvalue problem, so he didn't accept the Bohr-Rutherford atomic model. In the 1920's he and Werner Heisenberg developed the electron cloud model. (see Heisenberg for the cloud model)

//JJ Thomson (England) (1856-1940)://

In 1897, J.J. Thomson thought of the Plum Pudding Model. It shows that an atom was a small sphere with a positive charge and negatively charged particles randomly in the atom. He also discovered the electron, and the Nobel prize in 1906 for physics.


 * [[image:chem11.JPG width="138" height="129" caption="1897"]] ||
 * 1897 ||


 * 1901 - 1915**.
 * Robert Millikan** (U.S.A.) 1868 - 1953

In 1910, Millikan correctly determined the charge of an electron by using the "falling-drop method." He also discovered that this quantity was constant for all atoms. This shows the atomic structure of electricity.

Henri Becquerel (France) 1852 - 1908

Becquerel made his famous discovery of natural radioactivity in 1903. Becquerel investigated whether there was any connection between X-rays and naturally occurring phosphorescence. He realized that they differed from X-rays because they could be deflected by electric or magnetic fields.He shared half the Nobel Prize with Marie Curie and her husband.



//Ernest Rutherford (New Zealand) (1871-1937)://

His famous experiment was the "Gold Foil Experiment". He shot particles at a sheet of thin gold foil and unexpectantly 1 in 8,000 shot back. He explained it as if he shot a bullet into a piece of paper, and it came back. In 1910, he came up with a nucleus in the center of the atom.



(England) 1891 - 1974
 * 1916 - 1950**.

The neutron is important because it helps stabilize the nucleus. In 1932 Chadwick discovered it. It made the mass of the element higher without adding electrical charge. The neutron was huge, but, hence the name, neutral. The atomic bomb was made with the help of this guy's discoveries.

(Denmark) 1885 - 1962 He created the model that has a positively charged nucleus surrounded by orbiting electrons (which have electrostatic attracting forces). This is Bohr’s Atomic Model. But electrons fall into the nucleus, meaning that all atoms and all matter is unstable. Because of this, Bohr decided that the electrons that travel in orbits have discrete quantized speeds, meaning they have quantized energies. So, electrons gain or lose energy by switching orbits.
 * 1950 - present.**

Rutherford and Bohr came up with this new idea of the atomic structure, using Rutherford's nucleus.



He is partially credited for creating the "Electron Cloud Model" He is very much credited in the scientific community.
The cloud model represents where the electron has probably been and where it is likely to be going. The red dot in the middle is the nucleus while the red dot around the outside is an electron. As the electron moves it leaves a trace of where it was. This collection of traces quickly begins to look like a cloud.

bibliography yo.