EK-1g

[vmp200]

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#27:
The electron configuration of Cu is:
A.) [Ar]4s(1) 3d(10)
B.) [Ar]4s(2) 3d(10)
C.) [Ar]4s(2) 3d(9)
D.) [Ar]4s(1) 3d(10)

Why is the correct answer A and not C????


thanks
VP

 

[vmp200]

Nevermind found the answer. if anyone wants to know here it is.

The electron configuration for scandium is [Ar]4s(2)3d(1). As electrons are added in titanium and vanadium the configuration is [Ar]4s(2) 3d(2) and [Ar]4s(2) 3d(3). The next element, chromium, would be expected to have a configuration of [Ar]4s(2) 3d(4), however this is not the case. It turns out that as a result of the similarity in energy of the 4s sublevel and the 3d sublevel in this group that an interesting phenomena occurs at chromium. Instead of [Ar]4s(2) 3d(4) the electron configuration is [Ar]4s(1) 3d(5). We might suggest that a half-filled d sublevel has extra stability. The next element, manganese, the additional electron is added to complete the half-filled 4s sublevel and the configuration is [Ar]4s(2) 3d(5). From iron through nickel ([Ar]4s(2) 3d(6), [Ar]4s(2) 3d(7), [Ar]4s(2) 3d(8)) the electrons spin-pair in the 3d sublevel. At copper another reversal occurs. The electron configuration for copper is [Ar]4s(1) 3d(10) not [Ar]4s(2) 3d(9). Zinc has an electron configuration of [Ar]4s(2) 3d(10).

taken from:
http://intro.chem.okstate.edu/1215/Lecture/Chapter11/Fri112098.html

 

[el.harpo]

I don't know whats in that link but as far as I know, whenever the d orbital can be half-full or completely full it will "borrow/steal" an electron from the s orbital. 2 half-full orbitals are more stable than 1 full and 1 not full. Also, a full d orbital is more stable than a full s orbital because d is much bigger (more electrons can be stable that way). Hope that helps.

 

[vmp200]

I don't know whats in that link but as far as I know, whenever the d orbital can be half-full or completely full it will "borrow/steal" an electron from the s orbital. 2 half-full orbitals are more stable than 1 full and 1 not full. Also, a full d orbital is more stable than a full s orbital because d is much bigger (more electrons can be stable that way). Hope that helps.

that helps thanks a lot
VP