Quantum Numbers QN

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Quantum Numbers (QN)
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1. Principal QN (n)

• Gives information about the size of the electron
  cloud.
• Known as shells or energy levels
• As n increases, orbital is larger
• As n increases, the electron has more energy
• n 1, 2, 3, 4
• K, L, M, N
• The closer to the nucleus, the lower n

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1. Principal QN (n)

• 2n2 maximum number of electrons on that shell
• On the K-shell, n 1, 2n2 2
• On the L-shell, n 2, 2n2 8
• On the M-shell, n 3, 2n2 18
• On the N-shell, n 4, 2n2 32
• On the O-shell, n 5, 2n2 50
• Etc., etc., etc

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2. Angular Momentum QN (l)

• Also known as secondary QN, subshell QN or
  azimuthal QN
• l 0 (n-1)
• Corresponds to the shape of the orbital

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2. Angular Momentum QN (l)

• If l 0, then s-shape
• If l 1, then p-shape
• If l 2, then d-shape
• If l 3, then f-shape

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2. Angular Momentum QN (l)
What do the shapes look like? http//jchemed.chem.
wisc.edu/JCEDLib/WebWare/collection/open/JCEWWOR00
9/orbitalshapes.html
http//colossus.chem.umass.edu/bvining/downloads/c
hemland2/OrbitalShapes.htm
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3. Magnetic Quantum Number (ml)

• ml l -l
• Gives information about the orientation
  (direction) in space

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3. Magnetic Quantum Number (ml)

• Examples

• If l 0, then ml 0

• If l 1, then ml -1, 0, 1

• If l 2, then ml -2, -1, 0, 1, 2

• If l 3, then ml -3, -2, -1, 0, 1, 2, 3

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3. Magnetic Quantum Number (ml)

• An orbital is a place where 1 pair of electrons
  may be found.

• If l 0 an s-shape holds 1 pair of e-s

• If l 1 a p-shape holds 3 pairs of e-s

• If l 2 a d-shape holds 3 pairs of e-s

• If l 3 an f-shape holds 5 pairs of e-s

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4. Electron Spin QN (ms)

• Indicates the electron spin
• ms ½ or ½
• Corresponds to clockwise or counterclockwise

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Pauli Exclusion Principle

• 2 electrons in the same atom cannot have the same
  set of 4 quantum numbers.

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Examples
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HW Problems
Pages 340 342 16, 20, 21, 22, 26, 28, 37, 38,
42, 45, 50, 52, 53, 60, 61, 62, 65, 68, 77, 78
Due Wednesday