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Atomic Theory. When looking at the History of the Atom. The Atom was always Neutral. Let’s Take a Trip Through Time!. Democritus 460 – 370 B.C. Greek Philosopher There are various basic elements from which all matter is made Coined the term “atom” which means indivisible

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Atomic theory
Atomic Theory

When looking at the History of the Atom.

The Atom was always Neutral.



Democritus 460 370 b c
Democritus460 – 370 B.C.

  • Greek Philosopher

  • There are various basic elements from which all matter is made

  • Coined the term “atom” which means indivisible

  • Everything is composed of small atoms moving in a void

  • Some atoms are round, pointy, oily, have hooks, etc. to account for their properties

  • Ideas rejected by leading philosophers because void = no existence


“Atomos” = “indivisible”

“The material cause of all things that exist is the coming together of atoms and void. Atoms are too small to be perceived by the senses. They are eternal and have many different shapes, and they can cluster together … By aggregation they provide bulky objects that we can perceive with our sight and other senses… There is no void in atoms, so they cannot be divided.”

Demokritos c. 460-370 BC



Antoine lavoisier 1743 1794
Antoine Lavoisier 1743-1794

  • French

  • Known as the “Father of Modern Chemistry”

  • Came up with Law of Conservation of Mass

  • He had discovered that mass is conserved within a chemical reaction. The mass of the products of a chemical reaction is always the same as the mass you started with.


John dalton 1766 1844
John Dalton1766-1844

  • Born in England

  • Introduced his ideas in 1803

  • Proposed the “Atomic Theory”

    • Each element is composed of extremely small particles called atoms

    • All the atoms of a given element are identical, but they differ from those of any other element

    • Atoms of different elements have different properties including different masses

    • Compounds are formed when atoms of more than one kind of atom combine

  • Taught at University of Manchester, was said to “see things differently than others”


Dalton s model
Dalton’s Model

The Cannonball Model


Michael faraday 1791 1867
Michael Faraday1791-1867

  • Born in England

  • Coined term “electrolysis” –used electricity on solutions to split water (1832)

  • Also moved a wire through a magnet to create an electrical current which lead to invention of generators (Industrial Revolution)


James clerk maxwell 1831 1879
James Clerk Maxwell1831-1879

  • Developed the Maxwell-Boltzmann kinetic theory of gases (1866). This theory showed that temperatures and heat involved only molecular movement.

  • Electromagnetic Fields


Dmitri mendeleev 1834 1907
Dmitri Mendeleev1834-1907

  • Russian

  • Developed the Periodic Table (1869)

  • His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties.

  • Left space for new elements, and predicted three yet-to-be-discovered elements including eke-silicon and eke-boron.

  • His table did not include any of the Noble Gases, however, which had not yet been discovered.


Henri becquerel 1852 1908
Henri Becquerel1852-1908

  • Discovery of Radioactivity (1896)

  • Coined the term “X-Ray”

  • For his discovery of spontaneous radioactivity Becquerel was awarded half of the Nobel Prize for Physics in 1903, the other half being given to Pierre and Marie Curie for their study of the Becquerel radiation


J j thomson 1856 1940
J.J. Thomson1856-1940

  • Discovered electron 1897 – Cathode Ray Experiment

  • Plum Pudding model 1904

    • Electrons in a soupof positive charges

  • Discovered isotopes 1913

  • Noble Prize in Physics (1906)



Marie sklodowska curie 1867 1934
Marie Sklodowska Curie1867-1934

  • Born in , Warsaw, Poland (November 7, 1867)

  • Studied Uranium

  • Discovered Radium and Polonium

  • She worked with radioactivity, x-rays in medicine, and changes in the atomic nucleus. Curie’s discovery in changes in the atomic nucleus led the way toward the modern understanding of the atom as an entity that can be split to release enormous amounts of energy.


Marie curie con t
Marie Curie (con’t)

  • Awarded Noble Prize in Physics (with H. Becquerel and Pierre Curie) in 1903. “in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel."

  • Awarded Noble Prize in Chemistry in 1911. "in recognition of her services to the advancement of chemistry by the discovery of the elements radium and polonium, by the isolation of radium and the study of the nature and compounds of this remarkable element."


Albert einstein 1879 1955
Albert Einstein1879 - 1955

  • Jew born in Germany

  • Developed the Theory of Relativity and specifically mass-energy equivalence, E = mc 2

  • Received the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the Photoelectric Effect.


Albert einstein
Albert Einstein

  • Became a United States Citizen in 1940

  • With Leo Szilard wrote a letter to then President FDR on Aug 2, 1939 that lead to the Manhattan Project. (Einstein did not help develop the Atomic Bomb other than to sign the letter)

  • Manhattan Project-brought together top scientists from the US, Britain, Canada and refugees of Nazi Germany to develop Nuclear Weapons


Robert millikan 1868 1953
Robert Millikan1868-1953

  • Born in Morrison, Illinois

  • “Oil Drop Experiment” (1909) Determined the charge and mass of an electron

  • Set out to determine the measurement of electrical charge with the use of x-rays. In the process of doing so he discovered the most persuasive evidence to support that electrons were basic particles, and that they all had the equal mass and charge.


Ernest rutherford 1871 1937
Ernest Rutherford1871-1937

  • Born in New Zealand

  • Nuclear Model 1910

    • Gold Foil Experiment

      • Atom is mostly empty space

      • Nucleus has a positive charge

  • Noble Prize in Chemistry (1908) “for his investigation into the disintegration of the elements, and the chemistry of radioactive substances”


Ernest rutherford 1871 19371
Ernest Rutherford1871-1937

  • doctoral student of Thomson 1895-1989

  • Physics Chair at McGill from 1898-1907 before returning to England and teaching at Manchester University

  • takes over Cavendish Chair of Physics from Thomson in 1919


Alpha particle experiment
Alpha Particle Experiment

Show the Gold Foil Experiment Animation


Rutherford model
Rutherford Model

Nuclear Model


H g j moseley 1887 1915
H. G. J. Moseley1887 - 1915

  • English Physicist

  • Using x-ray tubes, determined the charges on the nuclei of most atoms.

  • He wrote “The atomic number of an element is equal to the number of protons in the nucleus”.

  • This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. (1913)


Niels bohr 1885 1962
Niels Bohr1885-1962

  • Danish

  • Planetary Model 1913

    • Nucleus surrounded by orbiting electrons at different energy levels

    • Electrons have definite orbits

  • Utilized Planck’s Quantum Energy theory

  • Worked on the Manhattan Project (US atomic bomb)


Bohr s model
Bohr’s Model

Quantum Energy Levels

-Atomic Model has electrons found in specific energy levels.



Prince louis victor debroglie 1892 1987
Prince Louis-Victor deBroglie 1892-1987

  • educated and worked in France - BA in 1913 & graduate work after serving for France in WWI

  • his 1924 doctoral thesis introduced “wave mechanics” - the idea that the electron could be treated as a wave

  • 1929 Nobel Prize in Physics


Werner heisenberg 1901 1976
Werner Heisenberg 1901-1976

  • Born in Wurzburg, Germany

  • 1923 PhD in Munich

  • 1924-’25 works with Bohr in Copenhagen

  • establishes “quantum mechanics” when only 23 years old in 1925 - includes Uncertainty Principle

  • 1932 Nobel Prize in Physics

  • 1941 director of Kaiser Wilhelm Institute in Berlin - captured by US troops at end of WWII & sent to England; returns to Germany after the war


Erwin schr d inger 1887 1961
Erwin Schrødinger 1887-1961

  • Born and educated in Vienna; serves in Austrian Army in WWI

  • 1926 publishes “wave equation” model of electrons

  • Goes to Germany in 1927 but leaves in 1933 with rise of Nazis; ends up in Austria in 1937; recants opposition to Nazis but is harassed and escapes in 1938

  • 1933 Nobel Prize in Physics with Dirac

  • 1940 establishes Institute for Advanced Studies in Dublin


Ernst schr dinger 1887 1961
Ernst Schrödinger 1887-1961

Werner Heisenberg 1901-1976

  • Quantum Mechanical Model or the Wave Mechanical Model or the Cloud Model 1926

    The accepted way we presently look at the atom

    • Electrons found in a region (cloud) around the nucleus

    • Electrons are in probability zones called “orbitals”, not orbits and the location cannot be pinpointed

    • Electrons are particles and waves at the same time

    • Developed quantum numbers based on theories of Einstein and Planck



James chadwick 1891 1974
James Chadwick1891-1974

  • Born in England

  • Made the important discovery of neutrons (1932). A particle in an atom that held a neutral charge, neither positive nor negative. This discovery helped tell the difference between the atomic number and the mass number.

  • Was awarded the Nobel Prize in Physics in 1935

  • A student of Rutherford


Otto hahn 1879 1968 fritz strassmann 1902 1980
Otto Hahn 1879 – 1968Fritz Strassmann 1902 - 1980

  • Worked with Lise Meitner in Berlin, until Meitner was forced to flee Nazi Germany

  • Experimented by bombarding uranium’s heavy nuclei with neutrons- got unexpected results – lighter elements, such as barium, were produced.

  • Hahn is regarded as "the father of nuclear chemistry" and the "founder of the atomic age".


Lise meitner 1878 1968 otto robert frisch 1904 1979
Lise Meitner 1878 – 1968Otto Robert Frisch 1904 - 1979

  • Meitner, a physicist, worked for years with chemists Hahn and Strassmann to study the behavior of nuclei

  • Meitner, working with her nephew, Frisch, were the first to understand that uranium nuclei could be split when bombarded by neutrons.

  • Calculated the amount of energy released each time a uranium nucleus undergoes fission (an example of E = mc squared at work)


Glenn seaborg 1912 1999
Glenn Seaborg1912 -1999

  • American born in Ishpeming, Michigan

  • Through the years of 1937 to 1939 he published many scientific papers. He also discovered 10 atomic elements and one was even named after him, "seaborgium."

  • Noble Prize in Chemistry (1951) w/ Edwin McMillan “for their discovery in the chemistry of the transuraniumelements”

  • Suggested a change in the layout of the Periodic Table


Glenn seaborg con t
Glenn Seaborg (con’t)

  • Appointed Chancellor of the University of California at Berkeley in 1958

    • Named Marv Levy as the Head Football Coach in 1960 (a position he held until1963)

      "In 1944, Seaborg formulated the 'actinide concept' of heavy element electronic structure which predicted that the actinides – including the first eleven transuranium elements – would form a transition series analogous to the rare earth series of lanthanide elements. Called one of the most significant changes in the periodic table since Mendeleev's 19th century design, the actinide concept showed how the transuranium elements fit into the periodic table."

      Headed the plutonium work of the Manhattan Project (1942-1946)

      Co-discoverer of plutonium and all further transuranium elements through element 102

      Between 1961 and 1971, Seaborg was the chairman of the AEC, a predecessor agency of the Department of Energy (DOE). Seaborg was active in national service, advising ten presidents from Franklin D. Roosevelt through George H. W. Bush.


Enrico fermi 1901 1954
Enrico Fermi1901 - 1954

  • Italian

  • Used neutron to split the nucleus of uranium atom (First controlled chain reaction)

  • Fled Italy in 1938 and became a naturalized American

  • Lead Manhattan Project at University of Chicago


Manhattan project
Manhattan Project

  • Started because F.D.R was persuaded by Einstein and other scientist after Hilter’s assault on Poland

  • Brought together the top scientists from US., England, Canada, and refugees of Nazi Germany

  • Under the leadership of Enrico Fermi, took place at the University of Chicago’s Stagg Field (Football Field)

  • On July 16, 1945 in a desert near Alamogordo, New Mexico experts detonated the first atomic device.


World war ii
World War II

  • December 7, 1941

    Pearl Harbor

  • Potsdam Conference, held in Berlin in July 1945

    President Truman with J. Stalin issue a ultimatum to Japan, surrender or be destroyed

  • August 6, 1945

    Dropped bomb on Hiroshima

  • August 9, 1945

    Dropped bomb on Nagasaki

  • August 10, 1945

    Japan Surrendered


Review of atomic models
Review of Atomic Models

1803 – Dalton

Cannonball Model

1897 – Thomson

Plum pudding Model

1909 – Rutherford

Nuclear Model

1913 – Bohr

Planetary Model

Present

Wave – Mechanical Model


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