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1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½)

1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½) 2s only 2 electrons (2, 0, 0, ½) or (2, 0, 0, -½) 2p 6 electrons (2, 1, 1, ½) (2, 1, 1, -½) (2, 1, 0, ½) (2, 1, 0, -½). 1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½)

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1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½)

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  1. 1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½) 2s only 2 electrons (2, 0, 0, ½) or (2, 0, 0, -½) 2p 6 electrons (2, 1, 1, ½) (2, 1, 1, -½) (2, 1, 0, ½) (2, 1, 0, -½)

  2. 1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½) 2s only 2 electrons (2, 0, 0, ½) or (2, 0, 0, -½) 2p 6 electrons (2, 1, 1, ½) (2, 1, 1, -½) (2, 1, 0, ½) (2, 1, 0, -½) (2, 1, -1, ½) (2, 1, -1, -½)

  3. 1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½) 2s only 2 electrons (2, 0, 0, ½) or (2, 0, 0, -½) 2p 6 electrons (2, 1, 1, ½) (2, 1, 1, -½) (2, 1, 0, ½) (2, 1, 0, -½) (2, 1, -1, ½) (2, 1, -1, -½) 3d 10electrons

  4. 1s only 2 electrons (1, 0, 0, ½) or (1, 0, 0, -½) 2s only 2 electrons (2, 0, 0, ½) or (2, 0, 0, -½) 2p 6 electrons (2, 1, 1, ½) (2, 1, 1, -½) (2, 1, 0, ½) (2, 1, 0, -½) (2, 1, -1, ½) (2, 1, -1, -½) 3d 10 electrons 4f 14 electrons

  5. For the He atom, the electronic configuration is 1s2 The orbital diagram is: He 1s

  6. For the He atom, the electronic configuration is 1s2 The orbital diagram is: He 1s The two electrons occupying the same orbital are said to be “paired”.

  7. For the He atom, the electronic configuration is 1s2 The orbital diagram is: He 1s The two electrons occupying the same orbital are said to be “paired”. One value of ms corresponds to and the other value of ms corresponds to .

  8. Note that both the diagrams would be ruled out by the Pauli Exclusion Principle (both electrons in each box have the same values of msas well as the same values of n, l, and ml).

  9. 3. Lithium Since only two electrons can be placed in the 1s orbital, the third electron must enter the 2s orbital.

  10. Energy level order 5s 5p 5d 5f 5g 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s Energy

  11. 3. LiElectronic configuration is 1s22s1 The orbital diagram is: Li 1s2s

  12. 3. LiElectronic configuration is 1s22s1 The orbital diagram is: Li 1s2s The lithium atom has one unpaired electron. A substance which contains unpaired electrons is paramagnetic.

  13. 3. LiElectronic configuration is 1s22s1 The orbital diagram is: Li 1s2s The lithium atom has one unpaired electron. A substance which contains unpaired electrons is paramagnetic. Paramagnetic: The weak attraction to a magnet of a substance containing unpaired electrons.

  14. Comparison of the energies of 1s22s1 versus 1s22p1

  15. Comparison of the energies of 1s22s1 versus 1s22p1 Which is lower in energy, and can we rationalize why this is so, for a multi-electron atom?

  16. Comparison of the energies of 1s22s1 versus 1s22p1 Which is lower in energy, and can we rationalize why this is so, for a multi-electron atom? The 1s orbital is filled and electrons in this orbital lie close to the nucleus.

  17. Comparison of the energies of 1s22s1 versus 1s22p1 Which is lower in energy, and can we rationalize why this is so, for a multi-electron atom? The 1s orbital is filled and electrons in this orbital lie close to the nucleus. Both the 2s and 2p orbitals are “larger”, and an electron in either of these two orbitals will lie on average, further away from the nucleus than an electron in the 1s orbital.

  18. An electron in either the 2s or 2p orbital is said to be shielded from the nucleus by the 1s electrons.

  19. An electron in either the 2s or 2p orbital is said to be shielded from the nucleus by the 1s electrons. That is, an electron in a 2s or 2p orbital in the lithium atom would not see a nuclear charge of +3.

  20. An electron in either the 2s or 2p orbital is said to be shielded from the nucleus by the 1s electrons. That is, an electron in a 2s or 2p orbital in the lithium atom would not see a nuclear charge of +3. The shielding reduces the electrostatic attraction between the protons in the nucleus and the electron in the 2s or 2p orbitals.

  21. From experiment it can be shown that the electron density for the 2s electron near the nucleus is greater than for an electron in a 2p orbital.

  22. From experiment it can be shown that the electron density for the 2s electron near the nucleus is greater than for an electron in a 2p orbital. For this reason, the 2s orbital is said to be more penetrating than the 2p orbital.

  23. From experiment it can be shown that the electron density for the 2s electron near the nucleus is greater than for an electron in a 2p orbital. For this reason, the 2s orbital is said to be more penetrating than the 2p orbital. For the same principal quantum number n, the penetrating power decreases in the order s > p > d > f ….

  24. From experiment it can be shown that the electron density for the 2s electron near the nucleus is greater than for an electron in a 2p orbital. For this reason, the 2s orbital is said to be more penetrating than the 2p orbital. For the same principal quantum number n, the penetrating power decreases in the order s > p > d > f …. Since the stability of an electron in an orbital is determined by how strongly it is attracted by the nucleus, it follows that an electron in a 2s orbital will be lower in energy than an electron in a 2p orbital.

  25. 4. Beryllium For the Be atom, the electronic configuration is 1s2 2s2 The orbital diagram is: Be 1s2s

  26. 4.Boron For the B atom, the electronic configuration is 1s2 2s22p1

  27. 4.Boron For the B atom, the electronic configuration is 1s2 2s22p1 The 2p orbital must be used since no more than 4 electrons can be placed in the 1s and 2s orbitals.

  28. 4.Boron For the B atom, the electronic configuration is 1s2 2s22p1 The 2p orbital must be used since no more than 4 electrons can be placed in the 1s and 2s orbitals. The orbital diagram is: B 1s2s2p

  29. Note that the unpaired electron for the B atom may be in the 2px, 2py, or 2pz orbital. This follows from the fact that the three 2p orbitals are equivalent in energy.

  30. 6. Carbon The first 4 electrons will be 1s22s2 which leaves 2 electrons to be placed in the available 2p orbitals.

  31. 6. Carbon The first 4 electrons will be 1s22s2 which leaves 2 electrons to be placed in the available 2p orbitals. Some possibilities are: 2px 2py 2pz

  32. 6. CarbonThe first 4 electrons will be 1s22s2 which leaves 2 electrons to be placed in the available 2p orbitals. Some possibilities are: 2px 2py 2pz 2px 2py 2pz

  33. 6. Carbon The first 4 electrons will be 1s22s2 which leaves 2 electrons to be placed in the available 2p orbitals. Some possibilities are: 2px 2py 2pz 2px 2py 2pz 2px 2py2pz

  34. 6. CarbonThe first 4 electrons will be 1s22s2 which leaves 2 electrons to be placed in the available 2p orbitals. Some possibilities are: 2px 2py 2pz 2px 2py 2pz 2px 2py2pz 2px2py 2pz 2px2py 2pz 2px2py 2pz

  35. 6. Carbon The first 4 electrons will be 1s22s2 which leaves 2 electrons to be placed in the available 2p orbitals. Some possibilities are: 2px 2py 2pz 2px 2py 2pz 2px 2py2pz 2px2py 2pz 2px2py 2pz 2px2py 2pz 2px 2py 2pz 2px2py2pz 2px 2py 2pz

  36. Choices can be restricted to: 2px 2py 2pz 2px2py 2pz 2px2py 2pz

  37. To predict which one of the above will give the greatest stability, requires the use of Hund’s rule.

  38. To predict which one of the above will give the greatest stability, requires the use of Hund’s rule. Hund’s Rule: The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins.

  39. To predict which one of the above will give the greatest stability, requires the use of Hund’s rule. Hund’sRule: The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins. 2px2py 2pz This is the preferred configuration.

  40. Hence, for carbon the electronic configuration is 1s2 2s22px2py The orbital diagram is: C 1s2s 2px 2py

  41. 7. Nitrogen: The electronic configuration is 1s22s22px2py2pz The orbital diagram is: N 1s2s 2px 2py 2pz

  42. 7. Nitrogen: The electronic configuration is 1s22s22px2py2pz The orbital diagram is: N 1s2s 2px 2py 2pz Note that Hund’s rule appliesto get the lowest energy configuration.

  43. 8. Oxygen: The electronic configuration is 1s22s22px22py2pz The orbital diagram is: O 1s2s 2px2py 2pz

  44. 8. Oxygen: The electronic configuration is 1s22s22px22py2pz The orbital diagram is: O 1s2s 2px2py 2pz Hund’s rule appliesto get the lowest energy configuration.

  45. 8. Oxygen: The electronic configuration is 1s22s22px22py2pz The orbital diagram is: O 1s2s 2px2py 2pz Hund’s rule appliesto get the lowest energy configuration. It is known from experiment that oxygen atoms are paramagnetic.

  46. 9. Fluorine: The electronic configuration is 1s22s22px22py22pz The orbital diagram is: F 1s2s 2px2py2pz

  47. 10. Neon: The electronic configuration is 1s22s22px22py22pz2 The orbital diagram is: Ne 1s2s 2px2py2pz

  48. Maximum number of electrons that can be assigned to the various orbitals

  49. Maximum number of electrons that can be assigned to the various orbitals For each shell (with principal quantum number n) there are n subshells.

  50. Maximum number of electrons that can be assigned to the various orbitals For each shell (with principal quantum number n) there are n subshells. For example, if n = 3, there are three subshells (three values of l) having l = 0, l = 1, and l = 2, corresponding to 3s, 3p, and 3d.

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