Electron Configurations Page 3

– Similarly, the building-up principle is used to

– Completely filled subshells have exceptional

obtain the electron configurations for periods 5, 6

stability

and 7 (similar and even more drastic exceptions

Cu →

[Ar]4s

instead of [Ar]4s

are observed)

Electronic Structure and the Periodic Table

• The filling order of the orbitals can be

• The table is divided into s, p, d, and f blocks

obtained from the periodic table:

named by the last occupied subshell being

– The ns, np, (n-1)d and (n-2)f orbitals are filled in

filled

the n

period from left to right

• Electron configurations can be deduced from

– The filling order is ns < (n-2)f < (n-1)d < np

the positions of elements in the periodic table

– Outer shell principal quantum numbers equal

period numbers (F → 2

period, n=2)

– All elements in a period have the same noble-gas

core configurations ([He], [Ne], [Ar], …)

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