Fall+2008+MMA+McCormack,+Timeline

Kyle McCormack Lou McDonald Atomic History Timeline Chemistry



He lived in anciant Greece. Democritus came up with the idea that all matter is made up of small indivisible units, or atoms. He stated that they were to small to see and that they all held different characteristics such as weight, mass, and shape. Also Democritus believed that atoms held the properties of what they made up. So when the atoms formed clusters they would turn into something that you could see and had definite characteristics.
 * Democritus (~460 B.C. - ~370 B.C.)**

Democritis model - Atoms grouped together Democritus' model showed that everything in the universe was made up of tinier, invisible particles. He concluded that they were all spherical and that all these particles formed together to form much larger times. Certain particles would also weigh more than others while some shapes were built of more particles. The overall conclusion was that everything in the world was constructed of tiny, invisible, spherical particles.



Aristotle was a Greek philosopher who lived from 384-322 B.C.. He stated that the world was made up of four distinct elements. These elements he said, were what made up everything in the universe. He also came up with the idea that matter is made up of substance (one of his elements) and form ( the shape they take) Aristotle's five elements Aristotle's element diagram
 * Aristotle**
 * 1) Fire
 * 2) Earth
 * 3) Air
 * 4) Water

Epicurus was a Greek Athenian who spent many of his younger years studying philosophy,and the purpose of life. He concluded that all atoms and tiny elements are always moving. And that the speed of all these tiny spheres deducts how hot the temperature of them is. Epicturus also deducted that the universe is made up of an infinite space and that the only activity that goes on in this space is the movement of tiny atoms whether it be rapid or slow throughout that infinite space.
 * Epicurus 341-270 BC**



Dalton was an English chemist, who lived from 1766 - 1844. He took some of the first atomic weights, and also came up with a new theory about atoms. He was able to figure out atomic weights without the fine-tuned instruments available today. His views on atomic theory are called his five main points on atoms. They are as follows: He made these five rules to describe what an atom is and how they interact with each other.
 * John Dalton**
 * 1) Atoms cannot be created or separated into smaller particles; a chemical reaction just changes how they are grouped.
 * 2) Each element has its own unique atom that is different from all other elements atoms.
 * 3) Atoms can be grouped with other atoms to form compounds.
 * 4) All atoms of a given element are identical.
 * 5) Elements are made up of tiny indivisible units called atoms.

Roentgen was a German Physicist who accidentally discovered the x-ray in 1895. He lived from 1845-1923. He discovered the x-ray when he was experimenting with cathode rays and vacuum tubes. He noticed that the tubes had a ray coming out the back which had fluorescent qualities. He experimented with the new rays for a few weeks, and then used them to take an x-ray picture of his wives hand.
 * Wilhelm C Roentgen**

The first x-ray

Julius Plucker was a German mathematician and physicist.He moved to Paris in order to become a student at a prestigious school, shortly thereafter he became a math professor at the same school. In 1958 he published one of his researches on how a magnet reacts on the electric discharge in rare fired gases. He noticed it cause a fluorescent glow on the walls of the tube and the glow could move as long as an electromagnet was held up to it. Later on, this glow was shown to be produced by cathode rays, which would later be used in the discovery of the electron.
 * Julius Plücker** (16 June 1801 – 22 May 1868)

Between 1859 and 1861, Mendeleev worked on the capillarity of liquids and the workings of the spectroscope in Heidelberg. Shortly there after he wrote his first book and after began to associate elements based on chemical properties. He soon discovered there was a pattern that helped him develop the periodic table. They are measure by atomic mass, valences, and protons in the nucleus. Mendeleev discovered this pattern and established the first periodic table of the elements.
 * Dmitri Mendeleev** February 27 1834 – February 20 1907



Becquerel was a french physicist, who lived from (1852-1908). He was the first person to discover radioactivity. He was doing experiments to gain a better incite into how Roentgens x-rays work. While working with the x-rays he discovered that uranium salts on the photographic plates makes the plates become exposed through the radiation from the salts.
 * Henri Becquerel**



Thomson was a British physicist who lived from 1856 1940. He discovered the electron and also came up with the plum-pudding model for the atom. His early experiments involved cathode rays and saw that the ray would bend away from an electric field, indicating the charge was negative. He stated that the electrons were spread out over a positively charged area and that these structures were atoms. The plum pudding model is so named because it has a sphere of positive charge(the pudding) and negatively charged electrons(the plums) inside of it.
 * J.J. Thomson**

Thompson's Plum Pudding model Thompson's plum pudding model is a brief summary of how the atom is composed of its electrons. It says that the atom is composed of mostly empty space with tiny electrons floating around the sphere. The electrons are negatively charged so they equal out the other charge inside the atom.



Rutherford was a physicist that was born in New Zeland and worked in England. He lived from 1871 - 1937 He was the first person to discover that the electrons rotate around the nucleus of protons and neutrons in an atom. On that note, he is also the first person to theorize about neutrons being part of an atom to counter act the forces of the protons and electrons. His famous experiment was the the gold foil experiment. In this experiment Rutherford shot alpha particles at a strip of gold foil to see what happened. He thought that the particles would go right through because the electrons were too spread out to deflect anything. What he discovered was that some particles deflected away because there was a solid nucleus in the center of the gold atoms.
 * Ernest Rutherford**


 * __Rutherfords Gold Foil Experiment__**

Rutherford's gold foil experiment discovered that the atom has a strong dense region in the center of it. It shot tiny particles at the gold foil. Almost every single particle would go through the foil but every one in eight thousand would be shot right back because it was being stopped by some region. He deducted that there wasn't a strong electrical field being controlled by the atom's electrons, but there was alot of emptiness and a large center region in it. With this, he concluded his new theory for how the atom is. He saw it just as the planets were in the universe. He said that there was a center particle called the nucleus comprised of the positively charged protons and the neutral charged neutrons. Circling the nucleus were electrons that were negatively charge. These electrons were 1/2000 the size of the protons and neutrons and followed a strict circular path about the nucleus. The electrons equaled out the atoms charge and were what was gained and lost in a chemical reaction.

Rutherfords Model of the atom



Curie was a Polish chemist who lived from 1867-1934. She did most of her research with her husband in France. She was the first person to discover polonium and radium. Also she created the theory of radioactivity. When she was studying uranium, she used a mineral called pitchblende, which contained a lot of uranium, but also something for times as active as uranium. She was able to separate the substance from the pitchblende and discovered how radioactive it was. She called this new element radium, which is a radioactive decay product of uranium.
 * Marie Curie**

Pitchblende



Millikan was an American Physicist who lived from 1868-1953. He discovered the charge of one electron through the oil-drop experiment. The charge he obtained is 1.592e-19 coulomb. This became known as the elementary charge. The oil-drop experiment used droplets of oil, let into a tube with a uniform electric field running through it. The charged droplets were collected on a plate and then the charge on them was calculated.
 * Robert Millikan**

The oil drop experiment



**Albert Einstein 14 March 1879 – 18 April 1955 ** Einstein was a German Jew studying in high levels of Math and Science, but one who could not get into his college. He dropped out of hight school to directly apply for college to be turned down despite exceptional scores in math and science.He was a genios when it came to physics and came up with many thoeries such as the thoery of relativity and principle of relativity. He wrote a paper on how tiny objects tend to always move, thus supporting the atomic thoery and that all matter is always in constant motion.



Bohr was a Danish physicist who lived from 1885-1962. He described the atomic structure in detail and also worked on quantum mechanics, as well as the Manhattan Project with Robert Oppenheimer and Albert Einstein. His major contribution to the atomic structure, was that the atom had electrons orbiting around the nucleus in orbital shells. This model is only a modified version of Rutherford's model, and for the most part are grouped together and known as the Rutherford-Bohr model.
 * Niels Bohr**

This picture clearly shows how the orbital shells work and what the look like for a Sulfer atom

The Rutherford-Bohr model concluded that electrons revolve in orbits that don't emit any radiation; each electron in each orbit has a fixed amount of energy, with the outer orbits having stronger and stronger energy; electrons can jump from higher energy fields to lower ones causing a photon electromagnetic radiation such as light; and an electron may also absorb a photon of radiation and jump from lower energy to higher energy orbits. The Rutherford-Bohr model mostly concluded the actions of the electrons and how they react with other substances and within their own orbits.



Heisenberg was a German physicist who lived from 1901-1976. He is famous for his work in the field of quantum mechanics, and created the uncertainty principle, as well as described the atom through an equation. The uncertainty principle states that a particles momentum and position cannot be known at the same time. So the smaller the area the particle could be at, the more uncertain the momentum would be and, vice versa.
 * Werner Heisenberg**

James Chadwick was born in Bollington, Cheshire, where he attended many schools and a number of tech schools as well. He worked with Ernest Rutherford and also in a German POW camp during World War One. He spent many years of the war stuck in a lab being forced to work. After the war, Chadwick made the discovery of a neutral charged particle in the atom's nucleus called the Neutron. He then discovered the fission of Uranium 235 and was awarded the Nobel Prize. Chadwick later came to America to work on the Manhattan project because the discovery of the atomic bomb wasn't possible, it was "inevitable."
 * James Chadwick 1891-1974 **



Schrodinger was an Austrian physicist who came up with the cloud model of the atom, and also introduced wave mechanics to describe an atom through mathematics. He was also around Germany during the rise of Hitler to power, and publicly denounced Naziism. The cloud model of the atom states that an electron could be at any point in the cloud at any time.
 * Erwin Schrodinger**

Schrodinger's equation The Cloud model

The electron cloud model explained how atom share their protons. Electrons in the cloud do not travel in an orbital path, they travel in specific paths easily figured out by the Schrödinger equation. The path followed by these electrons can consist from figure eights about the nucleus to complicated arrays and patterns Within these electron clouds is where the electrons are lost and/ are gained in chemical reactions and the such.The cloud expands when it is coming towards a reaction and constricts back down when the reaction is minuscule or not apparent. The electron cloud is the cloud about the nucleus of the atom where the electrons float about.



The father of the atomic bomb, Oppenheimer, just like Einstein, immigrated to the United States from Germany and become a member of the Manhattan project. Oppenheimer graduated from Harvard and then continued his study in Europe for a number of years before beginning his work on the first atomic bomb. After completing the bomb, he began working for a nuclear power company in order to try to make nuclear energy out of tiny little atoms. He and his crew discovered a way to harness the energy from the fissioning of atoms in order to create energy with not too much waste.
 * J. Robert Oppenheimer (1904–1967),**