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Everything You Need To Know About Atoms

Everything You Need To Know About Atoms

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Everything You Need To Know About Atoms

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  1. Everything You Need To Know About Atoms (for this course)

  2. Tiny Bits • Before we talk about what atoms are made of and what they can do, you must know: • They are VERY light, • They are VERY small, • There are VAST numbers of them.

  3. Bromide Atoms

  4. Hydrogen on Graphene

  5. Crystal Lattice

  6. Photograph of a Single Molecule of Pentacene, used in solar cells 14 Carbon and 22 Hydrogen atoms

  7. Biggest Tiny Parts • Neutrons: N, heaviest, no electrical charge • Protons: P+,slightly less heavy, positive electrical charge • Electrons: e-, much lighter than neutrons or protons, negative electric charge • All three have a quantum mechanical quality called spin 1/2

  8. Smaller Tiny Parts • Neutrinos: n • Three kinds: electron ne, muon nm, tau nt • Weakly interactive • VERY low mass, no charge • Travel at the speed of light • (We’ll use these a little later)

  9. Atoms • Atoms have protons and electrons and, with one exception, neutrons • The simplest atom is hydrogen • 75% of the universe is hydrogen

  10. Flavors (Isotopes) of Hydrogen:Deuterium (D)--------Tritium (T)

  11. Helium • Two electrons, two protons, two neutrons • 24% of the Universe • (There is a flavor with only one neutron)

  12. As of June 2011, 114 different elements… • But hydrogen (H) and helium (He) are all we need for the most part

  13. straP yniT tseggiB • Antimatter! • Negative protons, positive electrons • Antineutrons more difficult to explain (antiquarks, CPT symmetry—not really necessary for our study) • When matter meets antimatter: annihilation! • (We’ll meet this later also)

  14. PET Scan Positron emission tomography

  15. It Takes Energy To: • Remove an electron from an atom: • Jam a proton and neutron together to make deuterium (D) • Jam an N and a D together to make a tritium (T) • Jam two Ts together to get He

  16. E=mc2 • Except for reactions that involve only electrons, nuclear processes are governed by that famous equation • It says that matter can be converted to lots of energy, and that energy can be transformed into matter • Making He out of H takes a lot of energy, but once it’s accomplished, you get more energy back

  17. Fusion • That last process is a form of fusion • Not to be confused with fission (taught in another course) • The reaction can be notated this way: T + T -> 4He + 2N • I will use this shorthand later on (and remind you of what it means)

  18. Other Examples • A reaction can emit energy in the form of a photon D + D -> 4He + g • A reaction can generate a neutrino P+ + P+ -> D + e+ + ne Don’t memorize these! They are just examples!

  19. And that’s all you need to know about atoms!