Electron configuration

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Electron configuration
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Electron configuration
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Element Atomic number Electron configuration
He 2 1s2
Ne 10 1s22s22p6
Ar 18 1s22s22p63s23p6
Kr 36 1s22s22p63s23p63d104s24p6
Xe 54 1s22s22p63s23p63d104s24p64d105s25p6
Rn 86 1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p6
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Short cut Core notation

• Core notation takes the electron configuration of
  the last noble gas and adds the additional
  electrons, in their perspective orbitals, to show
  the same electron configuration of the element

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Group 1 Group 6

O He2s22p4
S Ne3s23p4
Se Ar4s23d104p4
Te Kr5s24d105p4
Po Xe6s24f145d106p4
H 1S1
Li He2s1
Na Ne3s1
K Ar4s1
Rb Kr5s1
Cs Xe6s1
Fr Rn7s1
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Exceptions

• Cr and Cu
• Cr (d4) borrows 1 electron from s-orbital
• Cr (Ar 4s1 3d5)
• half filled d orbital is very stable
• Cu fully filled d orbital
• Cu (Ar 4s1 3d10)
• filled d orbital is very stable

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Electron configuration for ions

• Negative ion add electrons to the last unfilled
  subshell
• Positive ion -
• electrons in outermost shell are removed first
• Remove p before s before d- electrons

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• Classwork p 156 158 27 - 29