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Quantum model of an Atom Chapter 17

Quantum model of an Atom Chapter 17. 0 of 250. 10. I read Chapter 15 before coming to class. Yes, the whole thing. Nope, essentially none. Well some, more than ½. A little only. 250. 0. The wave nature of moving particles is interpreted as being.

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Quantum model of an Atom Chapter 17

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  1. Quantum model of an Atom Chapter 17

  2. 0 of 250 10 I read Chapter 15 before coming to class • Yes, the whole thing. • Nope, essentially none. • Well some, more than ½. • A little only.

  3. 250 0 The wave nature of moving particles is interpreted as being • An up and down path that the particle travels in as it moves. • A back and forth path that the particle travels in as it moves. • Not a traditional wave at all but instead is a function that tells us the probability of detecting the particle.

  4. Newton’s Laws ok Perspective large small fast slow Relativity Wave-Particle Duality

  5. 250 0 10 Standing waves are created when • Waves reflect and bounce back to where they started from. • Waves wrap around and come back to where they started from. • Both 1 and 2 are ways standing waves can be created.

  6. Standing Waves

  7. 2 Dimensions • It is easy to create standing waves in 2 dimensions as well. Two waves on a drum head A single wave on a drum head Three waves on a drum head

  8. Wrap standing waves around a point • These are patterns of vibration.

  9. Bohr Model Explained! • Take de Broglie’s waves and wrap them in a standing wave pattern around the nucleus. • Put one wave , then two waves, then three waves, etc and you exactly predict the location of the Bohr radii! A CRUDE representation!

  10. The Quantum Model of the Atom • Electrons are found in 3-D electron probability waves. • They do not orbit. Instead they exist in the locations given by standing wave clouds. • We call these wave clouds orbitals to reflect the fact that the electrons do not orbit like a planet.

  11. The shape and energies of the actual orbitals depend on the number of standing waves in the pattern. They are found from solving the Shrödinger Wave equation: h2 d2Y(x) 8 p2m dx2 + V(x) Y(x) = EY(x) Three Dimensional Atomic Orbitals Kinetic Energy + Potential Energy = Total Energy

  12. Orbital Patterns • One wave: • Electrons will resonate in one pattern, called an “s” orbital. • Two waves: • Electrons will resonate in two patterns, “s” and “p” orbitals s s p

  13. Orbital Patterns • Three waves: Electrons will resonate in “s”, “p” and “d” orbitals. One orbital s p d

  14. S Orbitals • All numbers of standing waves have “s” orbitals. • They are all round but their interiors are different. • Still, in each case there is just one orbital.

  15. P Orbital • P orbitals come in sets of 3, whether there are 2 waves or 3 waves or more.

  16. D Orbitals • D orbitals come in sets of 5, whether there are 3 waves or 4 waves or more.

  17. Orbital Patterns • The pattern continues on as s, p, d, f, g, h, i, j, etc. Each new orbital set has two more orbitals than the previous one.

  18. e - e - The Pauli Exclusion Principle • At most two electrons can occupy the same orbital. If two electrons are in the same orbital, they must have different spins. Spin Down Spin Up

  19. High energy Low energy 1 2 3 Understanding Atoms • How do electrons fill the orbitals as we move along the periodic table? • Electrons fill the lowest energy levels first. For the lighter atoms, fewer standing waves and simpler orbitals usually means lower energies. • From here on I’ll refer to number of standing waves (physics lingo) as energy levels or shells (chemistry lingo).

  20. Electrons in an Atom: Energy WellsFill the lowest energy orbitals first free electron Zero Energy 3d 3p 3s Level 3 2p Level 2 2s Energy It is negative for a bound electron Level 1 1s

  21. Hydrogen free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  22. Helium free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  23. Lithium free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  24. Beryllium free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  25. Boron free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  26. Carbon free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  27. Nitrogen free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  28. Oxygen free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  29. 250 0 What is the maximum number of electrons in the entire set of p orbitals of any given shell? • 1 • 2 • 3 • 6

  30. 250 0 10 How many orbitals all together are in the third shell by itself? • 3 • 5 • 9 • 16

  31. 250 0 10 How many electrons total are in an atom that has the first and second shells completely filled? • 4 • 6 • 10 • 12

  32. Absorption line spectra revisited • The outer electron of any atom can jump up to higher orbitals creating a unique absorption spectrum for that element free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

  33. Emission line spectra revisited • It can then fall down creating the emission spectrum for that element. free electron 3d 3p 3s Level 3 2p Level 2 2s Level 1 1s

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