[Josette017]

The following problem is in my Chemistry book...

Write the orbital diagram corresponding to the ground state of Nb, whose configuration is [Kr]4d⁴5s¹.

I look at this and find Nb's configuration to be [Kr] 5s²4d³.

Am I wrong about this or is the book wrong?     


Thank you for your help

[lost and found]

My sources say that the book is right 

Nb = [Kr]4d⁴5s

[champ]

the book is right because block "d" elements lose block "s" electrons first. so thats why the configration of Nb is
Nb = [Kr]4d45s

[agrobert]

the book is right because block "d" elements lose block "s" electrons first. so thats why the configration of Nb is
Nb = [Kr]4d45s

Not exactly

http://en.wikipedia.org/wiki/Electron_configuration#Exceptions_in_3d.2C_4d.2C_5d

[serdi]

Why Nb 's configuration [Kr] 5s¹ 4d⁴ ? there is no half filled shell? I expected like [Kr] 5s² 4d³ as Josette?

[Borek]

IMHO these are fineprints that are not worth looking at for exact explanation. Thing is, energy levels of these configurations are very close. We are comparing huge numbers (energy) that differs by small amount. Sometimes effect of half orbital being filled wins, sometimes effect of full oribital wins. For me looking for hard rules here is not worth much more then numerology. These are just excpetions and should be treated like ones.