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Chapter 5

Chapter 5. Models of the Atom. Bohr’s model…. Electrons are found in specific circular paths (orbits) around the nucleus. The electrons have fixed energies called energy levels. (like rungs on a ladder)

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Chapter 5

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  1. Chapter 5 Models of the Atom

  2. Bohr’s model… • Electrons are found in specific circular paths (orbits) around the nucleus. • The electrons have fixed energies called energy levels. (like rungs on a ladder) • The amount of energy required to move an electron to another energy level is called a quantum.

  3. The Quantum Mechanical model • It is based on the energy and possible location of an electron. • how likely it is to find an electron is described in terms of probability. (ie. Propeller blades) • Based on work done by Shrodinger…

  4. Atomic Orbitals • The energy levels of electrons are labeled by principal quantum numbers (n) • Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

  5. Atomic Orbitals

  6. Shapes and Orientations of Orbitals

  7. 1s Orbital • Sphere around the nucleus The one tells you that the electron is in the orbital closest to the nucleus • S tells you about the shape

  8. 2s Orbital • Similar to 1s except the electron is most likely in the region farther from the nucleus

  9. p Orbitals • At the first energy level there is only the 1s orbital, after the second energy level there are 2p orbitals • Look like dumbbells • In the three directions

  10. Remember….MAX NUMBER OF ELECTRONS IN AN ENERGY LEVEL

  11. Electron Configuration A detailed way of showing the order in which electrons fill in around the nucleus

  12. Electron Configuration Symbols 1s2 # of e- in sub level Energy Level Sub Level (s, p, d, f )

  13. We must follow 3 rules… • Aufbau priciple • Electrons occupy energy levels with lowest energy first.

  14. Pauli exclusion principle • If 2 electrons occupy the same energy level they must have opposite spins.

  15. Hund’s rule… • Electrons that occupy orbitals of the same energy will have the maximum number of electrons with the same spin. • 2p

  16. To start we will use orbital filling diagrams to help us with electron configurations…. • Example Boron- has 5 electrons

  17. Periodic table arrangement • the quantum theory helps to explain the structure of the periodic table. • n - 1 indicates that the d subshell in period 4 actually starts at 3 (4 - 1 = 3).

  18. Practice!!!

  19. Summary: p orbitals and d orbitals p orbitals look like a dumbell with 3 orientations: px, py, pz (“p sub z”). Four of the d orbitals resemble two dumbells in a clover shape. The last d orbital resembles a p orbital with a donut wrapped around the middle.

  20. 1st Quantum # Principle Quantum # (n) Specifies the energy level that the electron is on.

  21. 2nd Quantum # (l) Specifies the shape of the sub level .

  22. The 3rd(m) and 4th quantum numbers (s) … • Deals with the orbital within the sublevel and the spin of the electron.

  23. Four Energy Sub-Levels

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