Evolution of the Atomic Theory

Evolution of the Atomic Theory.

Mudassir- Shafin- Jashanjot

Dimitri Ivanovich Mendeleev

Antoine Laurent Lavoiser

ROBERT BOYLE'S LAW

Mendeleve (1837-1907) was a chemistry professor at the univeristy of St.Petersburg in Russia. He is widely known for making the periodic table.

An Irish scientist Robert Boyle (1627-1691) was an experimenter. He is widely known for Boyle's Law in which he states that gas pressure and volume are inversly related. Decrease the volume of a gas, and you increase it's pressure and vice versa.

Lavoiser (1743-1794) was a French chemist who is most commonly known for his law of conservation of mass, which states that no mass is created or destroyed in a chemical reaction. Thus the weight before and after a chemical reaction will always be the same. He made this discovery, mainly because of Henry Cavendish (1731-1810) that water is a compound made up of oxygen and hydrogen.

Henry Mosely

Joseph Gay-Lucassac

Joseph John Thomson

Lucassac (1778-1850) used electrolysis to determine the exact volume of hydrogen and oxygen that made up water. He found out that if the atomic weight of hydrogen were set at 1, then oxygen had to be 16, not 8 which was proposed by John Dalton.

Henry Mosely (1887-1915) was a British physicst. He bombarded electrons on different types of metals, and measured if it affected the frequency of x-rays they produced. Through this he was able to find the atomic number.

J.J. Thomson (1856-1940) was a Cambridge graduate and student of James Clerk Maxwell. In 1897 ,he repeated the cathode ray experiment and used magnetic field to determine the existent of electron in an atom. He though that the atom was a postive matrix, with electrons scattered in it. Just how blueberries are spread in a raisin bun. And thats why the atomic model of Thomson is known as rasin bun.

Wilhelm Roentgen

J.J Berzelius

Louis de Broglie

Murray Gell-Mann

Roentgen was a German physicist. He discovered that electricity running through crooks tube produced powerful rays that would expose photographic films even if it was wrapped in a material that prevented the access of light. He called them X-RAYS

Niels Bohr

In 1923, Louis (1892-1987) studied Einstein's theory that matter and energy were equivalent. He discovered that electrons while having some properties of particles, also composed of "matter waves." So they moved around the nucleus like waves, not being confined to a particular place in empty space.

J.J Berzelius (1779-1848) was a Swedish chemist. He is credited with the discovery of the elements cerium, selenium, silicon, and thorium. He also prepared a table of elements with accurate atomic weights.

Murray in 1963 proposed that all subatomic particles were made of even more smaller particles which he called "quarks". He devised that quarks were fundemental in building blocks of matter. There were six of them, which were called (up, down, charm, strange, top and bottom)

Frederick Soddy

Frederick Soddy (1877-1956) worked with Rutherford. He devised the term "isotopes" to describe the variations of the basic element. He studied the radioactive decay of the element thorium and observed that it transfomed itself into a different version of thorium with the exact chemical properties, but different atomin weights. This observation confused scientists and threatned to invalidate the elgent organiztion of Mendeleev's periodic table. How can an element have 2 different atomic weights?

Niels Bohr worked under J.J. Thomson in Cambridge and under Earnest Rutherford in Manchester. In 1916 he became interested in the quantum theory. He expanded Rutherford's atomic model. He discovered that when an electron absorbs a quanta of energy, it jumps to a higer orbit or energy level. When it jumps back to it's original energy level, the electron emits energy in the form of a photon.

Discovery of Antiprotons

Anti protons were discoverd in 1950. They were like protons, but they were proton's anti partical.

Max Planck (1858-1947)

Discovery of Antineutrons.

Antineutrons were discovered in 1960. Antineutrons differs from the neutron only in that some of it's properties have equal magnitude, but opposite sign.

Discovery of Positron

Plank was trying to solve a problem in a way objects radiated energy when they were heated. In 1900 Planck announced hin new quantum theory, which states that objects emit energy in tiny discrete packets, rather than as continuous waves. But the amount of energy in the packet is related to the frequency detected when the wavelike qualities of energy are measured. He called these tiny packets as "quanta"

Henri Becquerel

Positrons were identical to electrons in every way, except it had an oppposite electric charge.

Discovery of the Last Quark

Werner Heisenberg

Henri Berquerel (1852-1908) was a French physicist. He became interested in the x-rays and tries to reproduce them. He found that uranium also produced these rays that could expose photographic films. But they weren't x-rays. He found a completly new kind of energy. Marie Curie had called them "radioactivity"

Amedeo Avogadro

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Heisenberg (1901-1976) studied the word of Bohr. In 1927, he presented his "uncertainty principle" which states that you cannot simultaneously measures both the position and the momentum of an object with complete accuracy. With large objects, the inaccuracy is very small, but with subatomic particles, the inaccuracy is significant.

In 1995, at the Fermi National Accelerator Laboratory near Chicago finally found evidence of the top quark, the last quark to be discovered. The discovery of these quarks provides proof of what physicst now call the Standard Model of atomic structure.

Earnest Rutherford

Avogadro (1776-1856), is most commoonly knwn for his law which states that under identical conditions of temperature and pressure, all gases of equal volume contain an equal number of "particles."

William Crookes

Earnest Rutherford (1871-1937) was a New-Zelander. He was an assistant of J.J. Thomson. Thomson and Rutherford became interested in x-rays, and Thomson asked Rutherford to investigate. Rutherford discovered tht uranium releases 3 types of rays (Alpha rays, which were positively charged. Beta rays, which were negitively charge, and gamma rays, ehich were neutral.) Rutherford used alpha rays to explore the inner structure of the atom. He experimented with gold foil and concluded that atoms are made up of mostly empty space, and in the centre of the atom, there is a tiny but dense positively charged particles which he called the nucleus. with further investigatioin, he was able to distinguish positively charge particles in the nucleus. He called them protons.

John Dalton

JOSEPH PRIESTLEY

Crookes (1832-1919) was an English chemist. He investigated the effects of gas pressure on the flow of electricity. For this he needed a sealed glasstube with a better vacuume in it than ever. He created an earlier version of the cathode ray tube which was called Crookes tube, named after him. He discovered the cathode rays.

Democritus

Joseph Preiestley (1733-1804) was interested in Carbon Dioxide and found a way to add it into water, producing the first carbonated beaverage and earned several awards as the inventor of soda pop. Preisestley most important work was his discovery of oxygen.

John Dalton (1766-1844) was an English Quaker and school teacher. He greatly contributed in the theory of atoms as he proposed that every substance is made up of combination of atoms of different substance, each with different mass and size, which could nither be created, nor destroyed. He also proposed how an atom might look like. His atom was a plain sperical ball, which wasn't divisable.

Atomic Models Over Time

Democritus (460 BC-370 BC) in 440BC proposed that every thing is made up of tiny particles, surrounded by empty space. He also said that they vary in size and shape depending on the substance they compose. He called these particles 'atomos" greek for indivisable. His idea was opposed by the popular philosophers of his day. Including Aristotle who said that matter was made up of earth, fire, water and air. Aristotle's influece holded science back for thousands of years. This gave rise to Alchemy, and during the middle ages, the alchemists took over the study of matter.