Electron Configuration
cont’d
MS. MCGRATH
CHEMISTRY 11
Aufbau principle
• States that in going from a hydrogen atom to a larger
atom, you add protons to the nucleus and electrons to
orbitals
• You start at the orbitals having the lowest energy level
and fill them, in order of increasing energy, until you run
out of electrons
Pauli exclusion principle
• States that an orbital can be empty, have one electron,
or at most have two electrons
Hund’s rule
• States that electrons in the same sublevel will not pair
up (occupy the same orbital) until all the orbitals in the
sublevel have been at least half filled
Electron configurations
•The lanthanides are the 14 elements removed from period 6 of
the periodic table
• The actinides are the 14 elements removed from period 7 of
the periodic table
• The above two groups do have unique electron configurations
Electronic configuration - Lanthanides
Lanthanum, atomic number 57:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1
or shorthand notation:
[Xe]6s2 5d1
Electronic configuration - Lanthanides
Erbium, atomic number 68:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 4f11
or shorthand notation:
[Xe]6s2 5d1 4f11
Electronic configuration - Lanthanides
Hafium, atomic number 72:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 4f14 5d1
or shorthand notation:
[Xe]6s2 5d1 4f14 5d1
Electronic configuration - Lanthanides
Note:
We place one electron in 5d then we fill up 4f with fourteen
electrons then return to 5d and place the remaining nine
electrons
Electron configuration - Actinides
Now you try:
Radium, atomic number 88
Uranium, atomic number 92
Rutherfordium, atomic number 104
Electron configuration - Actinides
Radium, atomic number 88:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 4f14 5d9 6p6 7s2
or shorthand notation:
[Rn]7s2
Electron configuration - Actinides
Uranium, atomic number 92:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 4f14 5d9 6p6 7s2 6d1 5f3
or shorthand notation:
[Rn]7s2 6d1 5f3
Electron configuration - Actinides
Rutherfordium, atomic 104:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 4f14 5d9 6p6 7s2 6d1 5f14 6d1
or shorthand notation:
[Rn]7s2 6d1 5f14 6d1
Electron configuration - Actinides
Note:
We place one electron in 6d then we fill up 5f with fourteen
electrons then return to 6d and place the remaining nine
electrons
Electron configuration - exceptions
Chromium and Copper
See video and make notes
Electron configuration for ions
Watch video and copy notes
Electron configuration for ions
Practice