Fall.2008.MMA.McCarthy.Timeline

__**Ancient Times 450 BC**__ 490-??? BC __Leucippus of Miletus__
 * 1) Greek philosopher. First to introduce the idea of the //atom//, an indivisible unit of matter. This idea was later extended by his student, Democretus.Is best known for paradoxes suggesting that motion is impossible because a magnitude can be divided into an infinite number of partfffffs, each of which must be traversed.

492-432 BC __Empedocles__ 2-Empedocles, of Acagras in Sicily, was a philosopher and poet: one of the most important of the philosophers working before Socrates.He attributed the invention of the four-element theory of matter (earth, air, fire, and water), one of the earliest theories of particle physics, put forward seemingly to rescue the phenomenal world from the static monism

460-370 BC __Democritus__ Greek philsopher, who developed the atomic theory of the universe. Democritus made many very important discoveries in the span of his lifetime but the greatest was that of the atom. He also said that everything in the world was made up of four element: Earth, Water, Wind, and Fire.

__**450-1700**__ 384-322 BC __Aristotle__ Greek philsopher, who was born in Stagira in the north of Greece.Aristotle provided us with knowledge of natural science including Physics, which gives a vast amount of information on astronomy, meteorology, plants, and animals.

1564-1642 __Galileo Galilei__ Galileo was a Italian physicist, Mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution.Galileo made the thermometer made of a sealed glass cylinder containing a clear liquid and a series of objects whose densities are designed to sink in sequence as the liquid is warmed and decreases in density.

1642-1727 __Sir Isaac Newton__ Isaac Newton was born in Lincolnshire and died in Kensington, London. He suggested an atomic theory in which atoms combined because of attractive forces between them to form solid, liquids and gases. He most famous discovery was of universal gravition.
 * __1700-1800__**

1743-1794 __Antoine-Laurent Lavoisier__ Lavoisier was a scienctist from France. He was one of the few chemists at the time to fully appreciate the importance of careful meaurements of reactants and products. In order to make such careful measurements he invented a balance which was to good to about .0005 grams. He proved the the Law of Conservation of Mass, showing that the mass of the reactants had to equal the mass of the products.

Oct.10, 1731-Feb. 1810 __Henry Cavendish__

In 1766 Cavendish was the fist person to discover factitious air. The first factitious air was inflammable air known today as hydrogen gas. The second was what he called fixed air, which is known today as carbon dioxide. Cavendish found their specific gravities and how much of the gas can be taken in by a liquid. Cavendish discovered that fixed air was not combustible and did not support life.

September 6,1776- July 27, 1844 __John Dalton__
 * __1800-1875__**

John Dalton originated the modern atomic theory in the eraly 19th century. He proposed the Atomic Theory in 1803 which stated that, all matter was composed of small indivisible particles termed atoms; atoms of a given element possess unique characteristics and weight, and three types of atoms exist: simple, compound, and complex.

1776-1856 __Amedeo Avogadro__ Avogadro, an Italian chemist, is most well known for his work on the molarity and Avogadro’s law. The number of atoms in one mole is 6.022x10 to the 23rd, for his work on this it was named Avogadro’s number. Avogadro’s law says, “The volume of a gas and the amount of the gas in moles are directly proportional.”

June 17th 1832-April 4th 1919 __William Crookes__ William lived in London and attended the Royal College of Chemistry. The Crookes tube was invented around 1875; it was a glass tube with a vacuum inside. An anode and a cathode attached to the ends. A current would travel in a straight line from the cathode to the anode. He found that this beam could be deflected by magnets and named it a cathode ray. This discovery would lead to the discovery of electrons by J.J Thompson. 1875-1900

Wilhelm C. Röentgen Born on March 27, 1845.Died on February 10, 1923. Country of Origin- Germany

Wilhelm C. Röentgen invented the x-ray on November 5th, 1985. Röentgen was doing an experiment in which he was observing the effects of a passing electrical discharge through gases at a low pressure. During this experiment he observed that he could see through everyday materials such as wood using a cathode ray. This was the bases for how the x-ray was founded which has been an incredible medical upgrade which can look at the human body**.**

Henri Becquerel  Born on December 15, 1852 Died on August 25, 1908 Country of Origin-France Henri Becquerel is known for his discoveries of radioactivity, in which he also won the Nobel Prize for. Becquerel’s first started doing research with the rotaion of plan-polarised light by magnetic fields. He then decided to turn to infra-red spectra. He studied certain elements such as Uranium and discovered that they were radioactive because of the atoms decaying.

J.J. Thomson J.J. Thomson was born on December 18, 1856. He died on August 30, 1940. Country of Origin-England J.J. Thomson or Sir Joseph John Thomas won the Nobel Prize for his discovery of an Electron in 1897. Sir J.J. Thomson was from the United Kingdom and attended Cambridge University in Cambridge, Great Britain. J.J. Thomas also discovered the Plum Pudding Model as shown above. This shows that the atom contains electrons surrounded by a cluster of positive charges to balance the electron’s negative charge. 1900-1915 Robert Millikan Robert Millikan was born on march 22, 1868, and died on December 19, 1953 Country of Origin-America Robert Millikan is known for his Nobel Prize winning for finding the measurement of a charge of an electron. He did this by using the “falling-drop method.” Millikan also studied many other scientist such as Albert Einstein, verifying Einstein’s all-important photoelectric equation.

Ernest Rutherford Ernest Rutherford was born on August 30, 1971. He died on October 19, 1937 Country of Origin-New Zealand Ernest Rutherford attended Cambridge University and worked with Professor J.J. Thomson. Mr. Rutherford invented a detector for electromagnetic waves. He also established the existence of the alpha and beta rays in uranium radiation and indicated some of their properties. Niels Bohr Neils Bohr was born on October 7, 1885. He died on November 18, 1962. Country of Origin-Denmark Niels Bohr attended Copenhagen University where he also studied under J.J. Thomson. He developed a model of a hydrogen atom and also a theory that states that electrons travel in certain orbits around the atom’s nucleus. The chemical properties of an element being determined mainly by the number of electrons present. The picture above is of the planetary model which was founded by Bohr and Rutherford in 1913 that shows a positive charged nucleus surrounded by electrons that orbit the nucleus. <span style="font-family: 'Times New Roman','serif'; font-size: 20pt; line-height: 115%;">1915-1950 <span style="font-family: 'Times New Roman','serif'; font-size: 20pt; line-height: 115%;">Erwin Schrodinger <span style="font-family: 'Times New Roman','serif';">Erwin Schrodinger was born on August 12,1887 and died on January 4, 1961. Country of Origin-Ireland <span style="font-family: 'Times New Roman','serif';">Erwin Schrodinger is famous for a paper he wrote called Quantisierung als Eigenwertproblem which was based on wave mechanics and is known today as the Schrodinger equation. This paper has been noted that it is the most important advances of the twentieth century and created major advances in both chemistry and physics.

<span style="font-family: 'Times New Roman','serif'; font-size: 20pt; line-height: 115%;">James Chadwick James Chadwick was born on October 20, 1891 and died on July 24 1974. Country of Origin-England <span style="font-family: 'Times New Roman','serif';">James Chadwick discovered the particle in the nucleus of an atom that became known as the neutron because it has no electric charg e. For this discovery he won the Nobel Peace Prize. Before his discovery he was in a German internment camp during World War I and there he was allowed to start his laboratory work. <span style="color: black; font-family: 'Times New Roman','serif'; font-size: 20pt; line-height: 115%;">Werner Heisenberg <span style="color: black; font-family: 'Arial','sans-serif';"> Werner Heisenberg was born on December 5, 1901 and died on February 1, 1976. Country of Origin-Germany <span style="font-family: 'Times New Roman','serif';">Werner attempted to detect electrons by interaction with protons. He created the Heisenberg uncertainty principle, which stated that it is impossible to determine both, the position and velocity of an electron or any other particle. <span style="font-family: 'Times New Roman','serif'; font-size: 20pt; line-height: 115%;">1950-Present <span style="font-family: 'Times New Roman','serif'; font-size: 20pt; line-height: 115%;">James Watson James Watson was born on April 6, 1928 and is currently still alive. Country of Origin-America <span style="font-family: 'Times New Roman','serif';">James Watson formed the structure of the double helix of DNA with help from other chemists. He also discovered many more advances in the chemistry field. As a child he had a serious interest in bird-watching, but this turned into a serious interest in genetics. After years of hard work and traveling from country to country to do research with new chemists across the world he won the Nobel Prize in 1962.


 * <span style="color: #e36c0a; font-family: Calibri; font-size: 26pt; font-weight: normal; line-height: 115%;">Small, spherical, solid, indivisible model **

<span style="color: #17365d; font-family: 'Times New Roman','serif'; font-size: 26pt; line-height: 115%;">The Electron Cloud

<span style="font-family: 'Times New Roman','serif';">

<span style="font-family: 'Times New Roman','serif';">The Electron Cloud model was really invented between three different scientists, Ernest Rutherford, Niels Bohr, and Werner Heisenberg. The model has a nucleus in the center, being surrounded by a number of electrons, it shows the probable locations of electrons in an atom. The model was formed as a comparison to the planets orbiting the sun.

**<span style="color: #d99594; font-family: 'Times New Roman','serif'; font-size: 26pt; line-height: 115%;">The Plum Pudding Model **

<span style="font-family: 'Times New Roman','serif';">

<span style="font-family: 'Times New Roman','serif';">The Plum Pudding Model was Invented by J.J. Thomson after the electron was founded. This model was founded in 1906 prior to the discovery of the anatomic nucleus. In this picture above it shows the black dots, which represent the negative charged electrons and the purple “pudding” represents the positive charged protons. The two balance each other out and this is supposed to be a metaphor to describe plums surrounded by pudding.

<span style="color: #0000cc; font-family: 'Arial','sans-serif'; font-size: 26pt; line-height: 115%;">The Rutherford-Bohr Model

**<span style="font-family: 'Arial','sans-serif'; font-size: 24pt; line-height: 115%;">Planetary Model **

The Bohr Model is probably familar as the "planetary model" is used as a symbol for atomic energy. In the Bohr Model the neutrons and protons occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun. This similarity between a planetary model and the Bohr Model of the atom ultimately arises because the attractive gravitational force in a solar system and the attractive Coulomb (electrical) force between the positively charged nucleus and the negatively charged electrons in an atom are mathematically of the same form. The form is the same, but the intrinsic strength of the Coulomb interaction is much larger than that of the gravitational interaction; in addition, there are positive and negative electrical charges so the Coulomb interaction can be either attractive or repulsive, but gravitation is always attractive in our present Universe.

<span style="font-family: 'Times New Roman','serif';">Work cited <span style="font-family: 'Times New Roman','serif';">Scientist <span style="font-family: 'Times New Roman','serif';">http://www.chemistry.co.nz/chronology.htm <span style="font-family: 'Times New Roman','serif';">http://www.chem.ucla.edu/chempointers.html <span style="font-family: 'Times New Roman','serif';">http://chemistry.about.com/cs/history/a/aa020204a_3.htm <span style="font-family: 'Times New Roman','serif';">http://nobelprize.org/ <span style="font-family: 'Times New Roman','serif';">Pictures <span style="font-family: 'Times New Roman','serif';">http://www.aps.org/publications/apsnews/200705/images/chadwick_web.jpg <span style="font-family: 'Times New Roman','serif';">http://www.wikipedia.org/