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Arrangement of Electrons in Atoms: The Quantum Model

Explore the development of a new atomic model, including electromagnetic radiation, the photoelectric effect, quantum theory, and electron configuration.

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Arrangement of Electrons in Atoms: The Quantum Model

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  1. Chapter 4 Arrangement of Electrons in Atoms

  2. I. The Development of a New Atomic Model • Electromagnetic Radiation: • “radiant energy” form of nrg that has wave characteristics and can travel through a vacuum “light” • Electromagnetic Spectrum: • Distribution among various wavelengths of the radiant nrg emitted or absorbed by an object

  3. Wavelength (): corresponding points on adjacent waves---Ex: Frequency (): # of waves that pass a point in a specific time • c = () () ------inversely proportional

  4. c = () () ------inversely proportional c : m/s  : m, cm, nm  : waves/second--Hertz (Hz)

  5. Photoelectric Effect: emission of e- by certain metals when light shines on them

  6. Quantum: min quantity of nrg that can be lost or gained by an atom • E = (h) () • J = (Js) (Hz) • Planck’s constant: 6.626 X 10-34 Js

  7. Video #15 (wave function and wave particle) • Einstein • dual wave-particle to describe light • Photon: radiation with zero mass carrying a quantum of nrg • packet of nrg emitted when an e- drops nrg levels

  8. Ground state: lowest nrg state • Excited state: higher potential nrg

  9. --Bohr’s Model-- • e- exist only in orbits with specific amounts of energy called energy levels • Therefore… • e- can only gain or lose certain amounts of energy • only certain photons are produced

  10. Line-Emission Spectrum excited state ENERGY IN PHOTON OUT ground state

  11. Bohr Model -Energy of photon depends on the difference in energy levels -Bohr’s calculated energies matched the IR, visible, and UV lines for the H atom 6 5 4 3 2 1

  12. Other Elements • Each element has a unique bright-line emission spectrum. • “Atomic Fingerprint” Helium • Bohr’s calculations only worked for hydrogen! ----pg 97

  13. II. The Quantum Model of the Atom • A. Electrons as Waves • Diffraction: bending of a wave as it passes by the edge of an object • Interference: results when waves overlap

  14. VISIBLE LIGHT ELECTRONS EVIDENCE: DIFFRACTION PATTERNS

  15. Video # 13(What is the Heisenberg Uncert) • Heisenberg Uncertainty Principle • Impossible to know both the velocity and position of an electron at the same time

  16. Video #14(Quantum Mechanics: Schrod) • SchrödingerWave Equation (1926) • finite # of solutions  quantized energy levels • defines probability of finding an e-

  17. A. Atomic Orbitals and Quantum Numbers • Orbital: probable location of an e- • Quantum #: properties of atomic orbitals and properties of e-’s in orbitals • Principal quantum #: (n), indicates main nrg level occupied by the e- • n = 1 -----occupies 1st nrg level

  18. Angular momentum quantum #: (l), indicates shape of orbital • Magnetic quantum #: (m), orientation of an orbital • Spin quantum #: which spin state (+)(-) • ***See table 4-2 pg 104

  19. Radial Distribution Curve Orbital • Orbital (“electron cloud”) • Region in space where there is 90% probability of finding an e-

  20. UPPER LEVEL • Four Quantum Numbers: • Specify the “address” of each electron in an atom

  21. 1. Principal Quantum Number ( n ) • Energy level • Size of the orbital • n2 = # of orbitals in the energy level

  22. s p d f 2. Angular Momentum Quantum # ( l ) • Energy sublevel • Shape of the orbital

  23. n = # of sublevels per level • n2 = # of orbitals per level • Sublevel sets: 1 s, 3 p, 5 d, 7 f

  24. 3. Magnetic Quantum Number ( ml) • Orientation of orbital • Specifies the exact orbitalwithin each sublevel

  25. 4. Spin Quantum Number ( ms) • Electron spin  +½ or -½ • An orbital can hold 2 electrons that spin in opposite directions.

  26. III. Electron Configuration • Aufbau principle: lowest nrg orbits fill first • Pauli exclusion principle: no 2 e-’s can have the same 4 quantum #’s. This is where spin allows 2 e-’s to be in the same orbit • Ex: 

  27. Hund’s rule: orbital of equal nrg are occupied by 1 e-, before any is occupied by 2 e-’s • Ex:  • Orbital Notation: ex: pg 107 • Electron Config Notation: pg 107 • Electron Dot diagram: ex

  28. Noble gases: • are inert • complete octet • --show ex----

  29. Table 4-3 pg 110 1. Principal #  energy level 2. Ang. Mom. # sublevel (s,p,d,f) 3. Magnetic #  orbital 4. Spin #  electron

  30. Feeling overwhelmed?

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