[th3plan]

ok guys i have a problem, im trying to review for a chemistry placement test and i dont understand why lets say u get to K (pottassium) 4s^1.  Why isnt it instead 3d^1 3p^6.  But instead it skips D and then goes to 4s^1.  Why??? :S im so confused

[Yggdrasil]

The 4s orbital is lower in energy than the 3d orbitals.

http://en.wikipedia.org/wiki/Aufbau_Principle

[th3plan]

Yggdrasil just to be sure S = 2 P= 6 D=10 F=14?  Thats the most they can hold if im correct ?  And one more thing , so like 5s is smaller then 4f and 6s is smaller then 5f if i understand your explanation right ?

[th3plan]

also why is Ge  written as 3d^10 4s^2 4p^2.  But instead not like 4s^2 4p^2.  some they write others they dont , what is the logic behind it >?


Thanks

[enahs]

http://www.physchem.co.za/Atomic/Electron%20Configuration.htm
http://www.fordhamprep.org/gcurran/sho/sho/lessons/lesson36.htm
http://library.thinkquest.org/10429/low/eleconfig/electron.htm



More practice:
http://preparatorychemistry.com/complete_electron_configuration_tutorial.htm

[Yggdrasil]

For atoms in the 4th period, the 3d electrons count as valence electrons.  Similarly, for atoms in the 5th period, 4d electrons count as valence electrons.  In general, electrons in the (n-1)d and (n-2)f orbitals count as valence electrons and should be shown on the electron configuration.