Whalley.Connolly.atomichistory.fall.2009

__Electron Cloud Model__ This theory states that an atrom consists of dense nucleus made of neutrons and protons. The nucleus is surrounded by electrons that exist in diferent clouds at various energy levels.

__Plum Pudding model__

In Thomson’s "Plum Pudding Model" each atom was a sphere filled with a positively charged fluid. The fluid was called the "pudding." Scattered in this fluid were electrons known as the "plums." Thomson suggested that the positive fluid held the negative charges, the electrons, in the atom because of electrical forces.

__Rutherford-Bohr model__ The Rutherford-Bohr model depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus.

__Planetary model__ The Planetary model for the atom had a number of essential modern features. Like a high central charge concentrated into a very small volume compared to the rest of the atom. It also contained the bulk of the atomic mass, and a number of tiny electrons orbiting around the nucleus like planets.

Ancient Times Democritus, was born in 460 BCE in Thrace. His atomic theory stated that all things were made up of atoms that are indivisible, indestructable, and will always be in motion. Also he said that between the atoms were empty space. Considered to be the father of modern science, during his life time he was not as well known as his fellow phillosopher, Plato

Aristotle lived and taught in Athens for the majority of his life. He started as a pupil of Plato (who was taught by Socrates), and for some time was a the teacher of Alexander the Great.He wrote on a great variety of subjects, varying from astronomy to abstract philosophy.Material was made of atoms with the exception of the Prime Mover(God). All existing things were atoms or empty space. Atoms were seen as all being the same size like grains of sand, always in constant motion. Atoms were building blocks while elements were fundamental substances.



(About 480 BC - 420 BC) Leucippus was a greek philosopher who was credited by Aristotle for originating the theory of Atomism. His successor was Democritus who is well known compared to Leucippus, and the only known writings of Leucippus left are //The Great World System// and //On the Mind//. His theory said that all matter is homogenous and consists of a bunch of small indivisible particles. It also states that atoms are constantly in motion and through collisions and regrouping forms various sorts of matter. ( [] )

__1700-1800__ Joseph BLack, born April 16, 1728 to 6th December 1799, was a physician, physicist, and chemist from scotland. He is known for discovering latent heat, carbon dioxide, and specific heat.He was the mentor for James Watt, and was a founder of thermochemistry. The chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after Him Joseph Black was the first person to isolate Carbon dioxide as a pure element, showing that air was made up of many different elements. This help support the atom theory and dismiss the theory that air was a pure element.

== Antoine Lavoisier born in 1743-1794, was a french Nobleman who futhered the sciences of chemistry and biology.Born to a wealthy family in Paris, he attended the College Mazarin, studying chemistry, botany, astronomy, and mathematics. He was killed in the French Reveloution at the age of 50.== ==Antoine Lavoisier abolished the phlogiston, theory came up with the first law of conservation od mass, and came up with an extensive list of elements. He also recognized and named oxygen and hydrogen. He reorganized chemical nomenclature.==

Charles-Augustin de Coulomb lived from June 14, 1736 – August 23, 1806. Coulomb came from a wealthy French family and attended college at the prestigious College des Quatre-Nations. There he studied as a mathmetician under Pierre Charles Monnier. He is most widley known for th si unit for charge named after him, coulomb, and for developing Coulomb's law. Coulomb's advances for the atom theory, was his research on the electrostatic forces of attraction and repulsion. Though he did not know it, these discoveries would later be used to come up with the proton and electron theory.

__1800-1875__ John Dalton (6 September 1766 – 27 July 1844) was born as a quaker in Cumberland England. As a fifteen year old boy, Dalton help run a small quaker school in Kenndel. Dalton was appointed a teacher of mathematics and natural philosophy at a college in Manchester. He remained in that position until 1800. He is best known for his the work he did in the development of the atomic theory, and his research into colour blindness. Dalton created five main points for his Atomic theory. 1.The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative atomic weights. 2.All atoms of a given element are identical. 3.Atoms of one element can combine with atoms of other elements to form chemical compounds 4.Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process 5.Elements are made of tiny particles called atoms

Johann Josef Loschmidt(1821-1895) - He was an Austrian scientist who studied in chemistry and physics. He studied in thermodynamics, optics, and electrodynamics. Loschmidt was a professor at University of Vienna in 1868 and he taught physical chemistry. He was also the first person to estimate the size of an atom. He performed many different experiments with different molecules and and elements. He estimated that there are 6.022 x 10^23 atoms of 12g of Carbon. He figured this out though experiments based on kinetic theory. ANother interesting fact about Loschmidt is that he calculated the path of an atom is based on diffusion rates.

Dmitri Mendeleev lived from (1834-1907). He was a Russian Chemist who is credited with creating the periodic table. He also was able to predict properties of elements that weren't even on the table. On March 6, 1969 he made a formal presentation to the Russian Chemist Society which, described atomic wieghts and valence. In his first periodic table he predicted 8 different elements from their atomic weights. An interesting fact about the table was that he said terrellium had a higher atomic weight then iodine, but he placed them in the wrong order in the table, which ended up being correct in the end. He also predicted that there were more elements called the Lanthanide's and the Actinide's and many people dismissed this idea but later on he was proven to be correct.

__1875-1900__

Ernest Rutherford (30 August 1871–19 October 1937) was a physicist who became known as the major player in nuclear physics, and lived in New Zealund. He was originally from Hornchurch, Essex England. He studied at Havelock School and then Nelson College and won a scholarship to study at Canterbury College. He discovered an atoms positive charge is concentrated in a very small nucleus. He also came up with the planetary model for the atom, through his discovery and interpretation of Rutherford scattering in his gold foil experiment. He was also the first person to split the atom in 1917

JJ Thompson was a British physicist and Nobel laureate, credited for the discovery of the electron and of isotopes. Also for the invention of the mass spectrometer. As for the atom,Thomson proposed a different model for the atom. He said that the tiny negatively charged electrons must be embedded in a cloud of positive charge. His model would be famously called the Plum Pudding Model.

Henri Becquerel was a French physicist, and the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics. In 1894, he became chief engineer in the Department of Bridges and Highways. Then in 1896, while investigating phosphorescence in uranium salts, Becquerel accidentally discovered radioactivity. The SI unit for radioactivity, the becquerel, is named after him.

__1900-1915__ Marie Curie was a pioneer in the field of radioactivity, the first person honored with two Nobel Prizes, receiving one in physics and one in chemistry. She was the first woman to serve as professor at the University of Paris. She is also reponsible for finding two new elements, polonium and radium. Under her direction, the world's first studies were conducted into the treatment of cancers by using radioactive isotopes.

Niels Bohr was a Danish physicist who made contributions to understanding the atomic structure and quantum mechanics. For this he received the Nobel Prize in Physics in 1922. Niels bohr worked with a top team of scientists on the Manhattan Project. He also came up with the Bohr Model: the theory that electrons travel in discrete orbits around the atom's nucleus. He was also a major advocate for peaceful use of nuclear energy.

Robert Millikan (1868 - 1953) Millikan was a physicist who won awards for finding the charge of an atom and for his work in photoelectric effect. Millikan was able to measure the charge of an electron with his oil drop experiment. The experiment consisted of him squirting droplets into a container with two plates in it, a positive plate on top and a negative plate on the bottom. If the droplets floated to the bottom it meant that they didn't have any electrons, but if they floated up or very slowly then they had a negative charge. He also won a nobel prize in 1923 for his photo electric effect.

__1915-1950__

Werner Hiesenberg (1901-1976) He was a German physicist who studied in quantum mechanics and is most famous for asserting the uncertainty principle of quantum theory. This was basically saying that the old theory of saying that a precise velocity and location of all objects is not true. When light hits and electron the light has a momentum that alters the electron and you cannot measure the velocity or the location of the electron.

Erwin Schrodinger (1887-1961) He was an Austrian physicist who became famous for his studies in quantum mechanics and the Schrodinger equation which he won the Nobel Prize for in 1933. Schrodinger took past ideas from Scientists like Hiesenberg and put them together and came up with this equation called the Schrodinger equation. Solving the equation can in principle predict the properties and reactivity of all atoms and molecules. The only problem is the equation is extremely difficult to solve for any atoms except for the very simplest atoms.

James Chadwick (1891-1974) Chadwick is an English Nobel Prize winner who happened to discover the Neutron. In 1932 Chadwick proposed that there was a neutral particle in the nucleus of an atom. Rutherford proposed this idea a decade before but was not able to prove that there were any other particles in the nucleus. For Chadwick's discovery he was awarded the Nobel Prize in physics in 1935.

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