Subshells and Orbitals

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Subshells and Orbitals

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Quantum Mechanics

• Describes the arrangement of electrons in atoms
  in terms of
• Main or principal energy levels (n)
• Energy subshells
• Orbitals (space occupied within the atom)

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Principal Energy Levels (n)

• Contain electrons that are
• Close in energy
• Similar distance from nucleus
• Have values of n 1, 2, 3, 4, 5, 6..
• Maximum number of electrons 2n2
• n 1 2(1)2 2
• n 2 2(2)2 8
• n3

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Energy Levels (Shells)

• A group of electrons in an atom all having the
  same principal quantum number (n)
• n 1, 2, 3,
• The first shell (n 1) is lowest in energy, 2nd
  level next and so on 1lt2lt3lt4
• The number of electron in each shell is limited
  to 2n2
• n 1 2n2 2
• n 2 2n2 ____

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Energy Levels for Electrons

• Some possible electron transitions for the first
  three energy levels are shown below. The
  negative value means that the electron in the
  atom has a lower energy than a free electron
• Energy Level Energy, E
• n3 ___________________ (-) 2.420 x 10?19 J
• n2 __________________ (-) 5.445 x 10?19 J
• n1 __________________ (-) 2.178 x 10?18 J

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Learning Check S1

• A. What energy change (J) takes place when an
  electron in a hydrogen atom moves from the first
  (n1) to the second shell (n2)?
• B. What energy change (J) takes place when the
  electron moves from the third shell to the second
  shell?

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Solution S1

• A. What energy change takes place when an
  electron in a hydrogen atom moves from the first
  (n1) to the second shell (n2)?
• 1.634 x 10-18 J of energy must be absorbed.
• B. What energy change takes place when the
  electron moves from the third shell to the second
  shell?
• (-5.445 x 10-19J ) - (2.2420 x 10-19 J)
  -3.025 x 10?19J will be emitted as electron falls
  from a higher to a lower energy state

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Subshells

• Energy sublevels within energy level
• All electrons in a subshell have the same energy
• Designated s, p, d, f ..
• Sublevel energy sltpltdltf

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Electron Locations

• Main
• Energy
• Levels Sublevels
• n4 4s, 4p, 4d, 4f
• n3 3s, 3p, 3d
• n2 2s, 2p
• n1 1s

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Sublevels in n 1,2, 3

• 3d
• n 3 3p
• 3s
• 2p
• n 2 2s
• n 1 1s

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Electrons Allowed

• All electrons in the same sublevel have the same
  energy.
• All 2s electrons have the same energy. All 2p
  electrons have the same energy which is slightly
  higher than the energy of the 2s electrons
• s sublevel 2 electrons
• p sublevel 6 electrons
• d sublevel 10 electrons
• f sublevel 14 electrons

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Electron Configuration

• List of subshells containing electrons
• Written in order of increasing energy
• Superscripts give the number of electrons
• Example Electron configuration of neon
• number of electrons
• 1s2 2s2 2p6
• main shell subshell

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Order of Filling

• Total energy of a subshell
• energy of the main shell the subshell
• The 4s energy lt 3d energy
• 4p ___
• 3d ___ (finishes the n3 shell)
• 4s ___ (starts the n4 shell)
• 3p ___
• 3s ___
• 2p ___
• 2s ___
• 1s ___

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Writing Electron Configurations

• H 1s1
• He 1s2
• Li 1s2 2s1
• C 1s2 2s2 2p2
• S 1s2 2s2 2p6 3s2 3p4

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Sublevel Blocks

• s1 s2 p1 p2 p3 p4 p5 p6
• 1
• 2
• 3 d1 - d10
• 4
• 5
• 6

f1 - f14
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Periodic Table and Electron Configuration

• Find the element on the periodic table
• Use the order of filling indicated across each
  period
• Groups 1-2 s level
• Groups 3-8 p level
• Transition d level
• Lantanides f level

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Learning Check S2

• Indicate if each configuration is (1) correct
  or (2) incorrect for potassium. Give an
  explanation for selection of 1 or 2. Explain
• why or why not?
• A. 1s22s22p63s1 1 or 2
• B. 1s22s22p63s23p6 1 or 2
• C. 1s22s22p63s23p64s1 1 or 2
• D. 1s22p83s1 1 or 2
• E. 1s22s22p63s23p7 1 or 2

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Solution E2

• For phosphorus, indicate if each configuration
  is (1) correct or (2) incorrect. Explain why or
  why not.
• A. 2, 2, 8, 5 2
• B. 2, 8, 3 2
• C. 2, 8, 5 1
• D. 2, 6, 7 2

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Learning Check S3

• Using the periodic table, write the complete
  electronic configuration for each
• A. Cl
• B. Sr
• C. I

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Solution S3

• Using the periodic table, write the complete
  electronic configuration for each
• A. Cl
• 1s2 2s2 2p6 3s2 3p5
• B. Sr
• 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
• C. I
• 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5

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Learning Check S4

• A. The final two notations for Co are
• 1) 3p64s2
• 2) 4s24d7
• 3) 4s23d7
• B. The final three notations for Sn are
• 1) 5s25p24d10
• 2) 5s24d105p2
• 3) 5s25d105p2

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Solution S4

• A. The final two notations for Co are
• 3) 4s2 3d7
• B. The final three notations for Sn are
• 2) 5s2 4d10 5p2

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Orbital

• A 3 dimensional space around a nucleus in which
  electrons are most likely to be found
• Shape represents electron density (not a path the
  electron follows)
• Each orbital can hold up to 2 electrons.

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s orbitals

3s
2s
1s
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Three p Orbitals

px
pz
py
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p subshell contains p orbitals

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d orbitals

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Learning Check S5

• A. Number of electrons in a p orbital
• 1) 1e 2) 1e or 2e 3) 3e
• B. Number of orbitals in a p subshell
• 1) 1 2) 2 3) 3
• C. Number of orbitals in 4d subshell
• 1) 1 2) 3 3) 5
• D. Number of electrons (maximum) in a 3d
  subshell
• 1) 2e 2) 5e 3) 10e

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Solution S5

• A. Number of electrons in a p orbital
• 2) 1e or 2e
• B. Number of orbitals in a p subshell
• 3) 3
• C. Number of orbitals in 4d subshell
• 3) 5
• D. Number of electrons in a 3d subshell
• 3) 10e