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The Atom

The Atom. Dr. M. Hazlett – Mandeville High School. The History of Atomic Theory. Although he was not the first, Democritus (around 400 B.C.) is usually credited with first

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The Atom

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  1. The Atom Dr. M. Hazlett – Mandeville High School

  2. The History of Atomic Theory • Although he was not the • first, Democritus (around • 400 B.C.) is usually • credited with first • hypothesizing that matter • was made up of tiny, • solid, indivisible things • which he called Atomos.

  3. However, not everyone agreed . . . Aristotle (around 330 B.C.) argued that everything in the universe was made up of the four basic elements of fire; water; air; and earth. His belief would become the foundation of science until the 1700s – and be defended by the Church under threat of death!

  4. Yet, some faced the threat of heresy and charged ahead to disprove Aristotle’s theory. • Robert Boyle (1661) wrote the book Skeptical Chymist • In this, he established that experimentation is the basis of knowledge and science • In his works, he theorized that since air can be compressed, it was made up of what he called corpuscles with spaces between them • This put the 4 element theory in jeopardy!

  5. Robert • Boyle – • like the • hair?

  6. The biggest break came in 1803 . . . John Dalton developed a true theory of the atom His theory stated: 1. All matter is made up of atoms 2. All atoms of the same element are the same 3. Different elements – different atoms 4. Chemical reactions (rxns) are the rearranging, combining or separating of atoms

  7. Dalton’s Periodic Chart

  8. Probably his most important contributions were: • The Conservation of Matterwhich states that matter can not be created nor destroyed, only transformed • Law of Definite Proportions and Multiple Proportions– all compounds and molecules have the same ratio or proportion of atoms in them

  9. The quest to understand the atom moves on. William Crookes Using a Cathode Ray Tube (CRT), he found some interesting particles in 1879 He shot an electrical charge through the CRT filled with argon (Ar) gas and saw a stream of particles These would turn out to be electrons (e-)

  10. J.J. Thompson(1897) • Using the CRT or Crookes Tube, he replicated Crookes work • He set up magnets on the tube and noted that the particle stream would bend towards the positive magnet • Hence – he determined that the electron has a negative charge

  11. Thompson then theorized about the atom and created what he called the “Plum Pudding Model”

  12. Robert Millikan (1909) • His famous oil drop experiment – where he misted oil between to electrically charged plates resulted in some interesting facts: • The mass of an electron is 9.10938215x 10-31 kg Or 9.109 x 10-28 g; Or 0.510998910 MeV/c2; Or 5.485799 0943 x 10-4 u • The charge of the electron is 1.602 x 10-19 Coulombs (a measure of electrical charge)

  13. Ernest Rutherford • In 1898 through 1911, using the Gold Foil Experiment, he helped explain about the atom and alpha (α)and beta (β)radiation • He determined that the nucleus of an atom has a positive component – the proton (p+) • Its mass is 1.672621637 x 10-27 kg; Or 938.272013 MeV/c2; Or 1.00727646677 u

  14. Ernest Rutherford • Alpha radiation is a Helium (He) nucleus consisting of 2 protons (p+) and 2 neutrons (n0) • Beta radiation is an electron (e-) or a neutrino • This occurs when a proton or neutron decays • no p+ + e- + antineutrino • p+  n0 + e+ + neutrino • neutrino has enough energy to go through 1 trillion miles of Pb

  15. There is one other type of radioactive particle, the gamma (γ) • These are produced by collapsing neutron stars in bursts and in nuclear explosions • A 10 second burst has more energy than our sun puts out in 10 billion years • Bursts last from 2 to 30 seconds and occur every 100 000 to 1 000 000 000 years

  16. Gamma radiation is deadly – altering and destroying cells in living tissueBruce Banner wouldnot look like this . . . . . . . . . . . . . But this!

  17. James Chadwick (1932) • Chadwick would complete our picture of the atom with his finding of the third subatomic particle – the neutron (n0) • It has no charge – it’s neutral • Its mass is 1.67492729 x 10 -27 kg; Or 939.565560 MeV/c2 ; Or 1.0086649156 u • However – as we will see – it is probably the most important particle in the atom!

  18. During the 1930s – atomic theory advanced immensely with the introduction of quantum theory and other scientific developments

  19. Neils Bohr (1930s) • Confirmed what others found that an atom will give off a particular light wavelength (λ) • Basically – each color (ROYGBIV) will reflect a different element’s atoms • He also proposed the “Planetary Model of the Atom” • The electrons orbit the nucleus like planets in a solar system • There are seven levels • The model is 3 dimensional

  20. Although he would be best known for his work on relativity – the connections of time and space – Albert Einsteinwould also contribute to the knowledge of the atom in the early 1900s 1. Brownian Motion– the movement found by botanist Robert Brown of pollen grains in a dish of water can be explained by the collision of water molecules with the grains and . . .

  21. 2. The Photoelectric Effectwhich helped explain that light can either be a wave OR a particle called a photon

  22. The photon is a packet of energy (a quanta) which is the elementary particle of the electro-magnetic interaction. It has no mass! Thus – Begins the QUANTUM MODEL!

  23. The Quantum Model • This model deals with what is really going on in the atom • It includes the wave and particle behavior of the atoms’ components • The model also expands upon the three basic elementary particles (the p+ , e- , and n0) to include the sub-particles (roughly 100) that make these up!

  24. Erwin Schrodinger (1932) • The electrons are moving at the speed of light (c) so you really can not determine their exact location • Can only have a probability as to its location at any given moment • The speed of the electrons creates a cloud around the nucleus (the electron cloud) which prevents us from seeing beyond it

  25. The Carbon Atom Electron Cloud

  26. Werner Heisenberg (1934) • Develops the Uncertainty Principle • Light from looking at an electron causes it to move • Must use statistical probabilities to determine electron locations • Electron locations can only be predicted

  27. Paul Dirac (1934) • Among his numerous contributions, the most interesting may be that of anti-matter • Confirmed decades after he first theorized about it • Anti-matter is composed of particles with the opposite charge of regular matter particles • For example – the electron has its positron

  28. ANTI - MATTER • Today – anti-matter is created in particle accelerators by colliding atoms together • Currently – about 1 to 10 ng are made per year • It would cost $300 000 000 000.00 to make just 1 mg of the stuff • That’s $100 quadrillion to make 1 gram and it would take 100 billion years at our present rate of technology

  29. If you mix anti-matter with regular matter you get a big • 1 kg anti-matter with 1 kg matter will result in an explosion of about 47 megatons or 47 million tons of TNT (Hiroshima was only 13 kilotons)

  30. Louis de Broglie • He figured out the wave-particleduality of the e- • Established the wave function of e- (Ψ) • When an electron jumps from its original ground state and moves up to an excited state and back again- it releases energy in the form of photons • A photon is an energy packet of light

  31. The Four Forces of the Universe • The Quantum model is concerned not only with particles, but with the forces that affect them and act between them • It examines the charge of the particle (+, - or 0); the spin (+1/2 or -1/2); the shape of the e- orbit; and the energy level that the electrons are found in (1 through 7) Let’s look at the forces first. . . .

  32. The Forces: • Strong Nuclear Force • This is the force that holds the nucleus together – binding the n0 to the p+ • It keeps the protons from repelling each other (+ and + don’t mix) • It is carried by a gauge particle called a gluon • It is the strongest of the forces

  33. 2. The Weak Force • It binds the particles that make up the n0 and the p+ • A neutron and proton are each made up of three smaller particles called quarks of which there are six types with three flavors (we’ll talk more about these in a moment) • The weak force uses bosons

  34. 3. The Electromagnetic Force • Electrical fields always have a magnetic field running perpendicular to it • The EM particle is the photon and the electron • It is what cause + charged particles to bond to negatively charged particles (the e- to the p+)

  35. 4. Gravity • This is the weakest of all the forces – yet it holds planets in alignment with their suns • It has no known effect on atoms and particles • If it has a particle, it will be called a graviton – but no one has found it yet • No one knows why – and I’m not telling anyone!

  36. The Particle Zoo – The Standard Model MATTER Fermions Baryonic Non-Baryonic Made up of Quarks Made of non-Quark particles 1/6 of Universe 5/6 of Universe Hadrons Mesons Leptons Made from 3 Quarks Made from 2 Quarks Includes e- , tau, Includes p+ and n0 Includes pions, kaons muons, dark and 20+ more and 30+ more matter and more

  37. Particle Review Hadrons Bosons Leptons Quarks: Fields: Electron, Up, Down, Photon – EM muon, tau, Strange, Top, Gluon – Strong neutrinos, Bottom and Z, W+/- - Weak etc. Charm  Graviton (?) - make p+ & n0 Gravity Charges: Red, Blue, Green

  38. Review . . . • Quarks (6 types - U, D, S, C, T, B) • If 3 Quarks = Hadron -If 2 Quarks = Meson • p+ made up of: U-boson-U-boson-D • n0 made up of: D-boson-D-boson-U • The Boson (W or Z) is the WEAK FORCE • The n0 held to p+ (and versa vice) by a Strong Force gluon [makes up the nucleus] and the nucleus held to e- by EM Force

  39. Next Stop . . . . . . • We need to examine Atomic Numbers, Ions and Isotopes • From there – we will move onto more details about the Quantum Model, e- Configuration and Orbits

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