A History of Atomic Theory And Structure

History of the Atom Not the history of atom, but the idea of Original idea began Ancient Greece (400 B.C.E.) Democritus - Greek philosopher (460-370 BC) Worked with his mentor Leucippus to develop first atomic theory.

History of Atom Felt that had to be the smallest piece making up everything For example: If you look at the beach...made of sand Couldn’t you cut the sand into smaller sand? Eventually - no Atomos - Greek for indivisible

Democritus’ (The Original) Atomic Theory All matter consists of invisible particles called atoms. Atoms are indestructible, solid - but invisible. Atoms are homogenous (all one phase). Atoms differ in size, shape, and arrangement. For example: Solids are made of small, pointy atoms. Liquids are made of large, round atoms. Oils are made of very fine, small atoms that can easily slip past each other.

Along comes another Greek Aristotle - Famous philosopher Said Democritus was wrong... Said - All substances are made of 4 elements Fire - Hot Air - light Earth - cool, heavy Water - wet Blend these in different proportions to get all substances

Who Was Right? Greek society was slave based Felt that beneath Famous to work with hands Means did not experiment Greeks settled disagreements by debate Aristotle was more famous Therefore, he won This caused people to ignore Democritus’ for more than 2000 years! During that time was when alchemists came to be.

Law of Conservation of Matter (Mass) Antione Lavosier (1743 - 1794) Matter cannot be created or destroyed under normal conditions.

Joseph Proust (1754-1826) Law of Definite Proportions (published 1794 - not accepted until 1812) - compounds are made in a definite ration by mass Law of Multiple Proportions - two compounds can be made by the same elements

John Dalton (1766-1844) English, public lecturer and teacher, 1803 Fun Fact - started teaching at the age of 12! Summarized results of his experiments and those of other’s Dalton’s Atomic Theory - combined ideas of elements with atoms

Dalton’s Atomic Theory All matter is made of tiny indivisible particles called atoms. Atoms of the same element are identical, those of different atoms are different. Atoms of different elements combine in whole number ratios to form compounds Chemical reactions involve the rearrangement of atoms. No new atoms are created, destroyed, or subdivided.

Fun Facts about Dalton When John Dalton died, 40,000 people attended his funeral procession. He discovered color blindness Still sometimes referred to as "Daltonism". He was, himself, afflicted with color blindness.

Michael Faraday (1791-1867) English, 1832 Studied the effect of electricity on solutions Coined the term electrolysis for splitting molecules with electricity He was not a proponent of “atomism”

John Newlands (1837 - 1898) English, 1864 Very FIRST periodic table Established the law of octaves, elements are arranged according to increasing atomic weight similar physical and chemical properties occur after each interval of seven elements. John Newlands (1837 - 1898)

John Newlands Newlands was one of the first to detect a pattern in properties of the elements Fun Fact - Newlands had to petition for credit to be given for his work! Text

Lothar Meyer (1830 - 1895) German, 1869 Contemporary of Mendeleev - created a PT at the same time. His was not widely accepted.

Dmitri Mendeleev (1834-1907) Russian, 1869 Arranged elements into the first accepted periodic table. Widely accepted because it was published in a textbook Predicted missing elements Determined that elements were a function of their atomic weights. Became known as periodic law

Mendeleev’s Periodic Table

Sir William Crookes (1832-1919) English, 1879 Discovered the properties of Cathode Ray Tube Note: CRT was MADE by J. Plucker in 1859 Rays travel in straight lines from cathode Causes glass to fluoresce Deflected by electric and magnetic fields The CRT is a vacuum tube with a voltage source flowing through it. (Pic next page) FUN FACT: CRTs used to be our TVs

CRT Voltage source - + Vacuum tube Metal Disks

GJ (George Johnstone) Stoney (1826-1911) Irish, 1894 Proposed the idea of a negative particle existing Wanted to call it the electron (DID NOT FIND IT)

Wilhelm Roentgen (1845-1923) German, 1895. Found that very penetrating rays from CRT Not were not deflected by magnetic field. Named them X-rays

Henri Becquerel (1852-1908) French, 1896 Discovered radioactivity - he defined as spontaneous emission from a nucleus By studying the effect of x-rays on photographic film

He proposed three types of radiation... The real definitions came later... Alpha Positive Radiation - High speed helium nucleus Beta Negative Radiation - High Speed electron Gamma Neutral Radiation - High Energy radiation

J.J. (Joseph John) Thomson (1856-1940) English physicist, 1897 Used CRT to discover the electron Did so by finding the charge to mass ratio He was also the first person to notice that the atom can be divided (First person to actually do it - not him)

Thomson’s Experiment Voltage source - +

Thomson’s Experiment Voltage source - +

Thomson’s Experiment Voltage source - +

- + Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end

- + Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end

- + Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end

- + Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end

By adding an electric field Thomson’s Experiment Voltage source By adding an electric field

By adding an electric field Thomson’s Experiment Voltage source + - By adding an electric field

By adding an electric field Thomson’s Experiment Voltage source + - By adding an electric field

By adding an electric field Thomson’s Experiment Voltage source + - By adding an electric field

By adding an electric field Thomson’s Experiment Voltage source + - By adding an electric field

By adding an electric field Thomson’s Experiment Voltage source + - By adding an electric field

Thomson’s Experiment Voltage source + - By adding an electric field he found that the moving pieces were negative

Thomson’s Experiment 1904, Said the atom was like plum pudding Called the ‘Plum Pudding Model’ of the atom A bunch of positive stuff, with the electrons able to be removed

Marie Curie & Pierre Curie (1867-1934) (1859-1906) Polish & French, 1898 Studied Uranium and Thorium and called their spontaneous decay process ‘radioactivity’ She and Pierre, husband, also discovered Polonium and Radium Fun Fact: While she died of illness, her husband was run over by a horse drawn cart. He slipped while crossing the street in the rain.

Ernest Rutherford (1871-1937) New Zealand, 1898 Studied radiation and labeled them alpha and beta radiation. (need to know for future experiment)

Frederick Soddy (1877-1956) English, 1903 Proposed the idea of isotopes Discovered half-life

Max Planck (1858-1947) German, 1900 Developed the idea of ‘quanta’ packets of energy

Richard Abegg (1869-1910) German, 1904 Discovered the inertness of Nobel Gases because of their stable electron configuration Fun Fact - Actually died at the age of 41, in a balloon crash

Albert Einstein (1879-1955) German, 1905 Explains the photoelectric effect Electrons are emitted from matter when they absorb energy from light. Developed E=mc2

Hans Geiger (1882-1945) German, 1906 Developed an electrical ‘clicker’ to register alpha emission Called a Geiger Counter

Lise Meitner & Otto Hahn (1878-1968) (1879-1968) Lise Meitner - Austrian Otto Hahn - German 1907, Worked together to discover that Uranium can cause nuclear fission without them we would not have nuclear power (and the world may never have experienced the nuclear bomb.)

Robert Millikan (1868-1953) American, 1909 Oil Drop Experiment Determined the charge and the mass of an electron

Geiger - Again 1909, Developed an experiment called the foil experiment discovered large angle deflections of alpha particles by thin metal foils Alpha particles - positively charged pieces given off by uranium Shot them at gold foil which can be made a few atoms thick

Florescent Screen Lead block Uranium Gold Foil

What he expected

What he got

Rutherford - Again Ernest Rutherford English physicist. Fun Fact - he had 11 siblings! Believed in the plum pudding model of the atom. 1911 - He interpreted the results of Geiger (1909) that showed that there must be a small dense core at the center of the atom. Thus disproving plum pudding

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How he explained it + Atom is mostly empty Small dense, positive piece at center Alpha particles are deflected by it if they get close enough +

Nucleus Theory The atom is mostly empty space Two regions Nucleus Surrounded by electrons Called Nuclear Model

Rutherford - Again 1914, suggests the ideas of protons in the nucleus Rutherford coins the term proton.

Henry Moseley (1887-1915) 1914, Determined the charges on nucleus Called this atomic number Used this to reorganize the periodic table based on atomic number Fun Fact: Died at the age of 27 during WWI Periodic Table Song

Neils Bohr (1885-1962) 1922 - (HONORS WILL DISCUSS IN DEPTH) Bright line spectrum Tried to explain presence of specific colors in hydrogen's spectrum Energy levels Electrons can only exist in specific energy states Ground State Excited State Developed planetary model electrons moved in circular orbits with specific energy levels

Louis de Broglie (1897-1987) 1923, Discovered that electrons have a dual nature - similar to particle and waves. Supported work done by Einstein.

Gilbert N. Lewis (1875-1946) Introduces the term photon quanta of light

Edwin Schrodinger (1887 - 1961) 1926 - Quantum Mechanical Model (modern day model) Electrons are in probability zones called orbitals not orbits and the location cannot be pinpointed Electrons are particles and waves at same time (using de Broglie) Developed quantum numbers based on theories of Albert Einstein and Max Planck (HONORS)

Werner Heisenberg (1901-1976) 1927, Heisenberg Uncertainty Principle You cannot know the velocity and position of a particle at the same time.

Friedrich Hund (1896-1997) Robert Milliken (1868-1953) German & American, 1928 HONORS ONLY - Introduce concept of molecular orbitals

James Chadwick (1891-1974) 1932 - Discovered neutrons Combined his work and others work - found that there was more mass in the nucleus than the proton Neutral particles in nucleus of an atom - mass close to proton Fun Fact - Student of Rutherford and Rutherford was a student of Thomson

Werner Heisenberg - Again (1901-1976) German, 1932 Revised Electron Cloud Model to include Neutrons Uses it to explain isotopes

Enrico Fermi (1901-1954) Italian, 1934 Uses beta decay to produces neutrinos no charge, subatomic particle extremely tiny mass. mass has never been measured accurately.

Carl Anderson (1905-1991) American, 1936 Discovers muon subatomic particle 207 x bigger than the electron same charge

Atomic Bomb Actually began in 1919 with Rutherford Ernest Rutherford, Albert Einstein, and Niels Bohr regarded particle bombardment as useful in furthering knowledge but “unlikely to meet public expectations of harnessing the power of the atom for practical purposes anytime in the near future.”

Einstein’s Letter to FDR 1939, FDR and advisors met to review Einstein’s letter “recent research on chain reactions utilizing uranium made it probable that large amounts of power could be produced by a chain reaction and that, by harnessing this power, the construction of "extremely powerful bombs..." (was conceivable.) Roosevelt became convinced of the value of exploring atomic energy.

Manhattan Project 1939, epic, secret, wartime (WWII) effort Design and build the world's first nuclear weapon. Used efforts of the world's greatest physicists and mathematicians Cost $20 billion (2 billion at the time)

Manhattan Project Over 90% of the cost was for building factories and producing materials less than 10% for development and production of the weapons. Grew to employ more than 130k people Note: Considerable controversy surrounds Heisenberg’s work for the German’s on atomic research during World War II.

Manhattan Project Driven by fear of Hitler's Germany Monumental project - but took less than four years Fission chain reaction from U and Pu that released the bombs' destructive energy. United States exploded a nuclear bomb over Hiroshima on August 6, 1945.

Murray Gell-Mann (1929 - present) Fun Fact: Entered Yale at the age of 15! 1964, Coined the term “quark” Quark = fast moving point of energy (every p and n are made up of three) The quark makes up the neutrons and protons in the nucleus It can never be isolated There are up quarks and down quarks They are 10-15mm in size 1969, awarded the Nobel prize in Physics for his contributions

Common Particles Proton - previous slide Neutron - previous slide Electron - previous slide you should know that the charge of proton and electron are not +1 and - 1 aka – Fermion Muon – 200x bigger than an electorn, negative charge Quark - previous slide Boson - particle with no spin, may be any number of particles in the same state.

Hadron Collider Hadron - composite particle made up of quarks held together by a strong force. Located @ CERN (European Organization for Nuclear Research) - located in Geneva, Switzerland

Hadron Collider Searching for Higgs boson particle (theorized in 1964) 2012 - CERN announces discovery of a new particle with properties consistent with Higgs boson after experiments The HB Particle has been referred to as the God particle B/c it makes up all mass