Destroyer Gen Chem # 84

[Dae204]

84. Which species has the most unpaired electrons?
a)NA
b)I
c)Fe
d)Cu
e)Cr

The answer is E

What I don't get is how Cu has 1 unpaired electron. The explanation says that the 3d subshell will fill first, then the 4s. Can someone explain this? Thank you so much

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[ADentalHopeful]

oh i can help!
i think!

I dno wut NA is..but:

I [Kr] 5s24d105p5 so 1 unpaired because one p orbital is missing an e-

Fe [Ar] 4s23d6 four unpaired

Cu [Ar] 4s13d10 so 1 unpaired

Cr [Ar] 4s13d5 so five unpaired

there is 4s1 because those are special ones, the Cr column and the Cu column take an e- from the s orbital...

so yes, answer is Cr.
and yes u have to remember 1st year chem! sucks, but u wanna be a dentist right!!

 

[osimsDDS]

The 3d subshell is very unstable, therefore the 4s orbital gives up its electrons for the 3d subshell to be stable...d orbitals would rather be half full meaning 5 will fill up or completely full meaning 10 will fill the subshell. Now knowing that, it is easy to see that basically all of the group 4B and 9B transition elements will take an s orbital electron away in order to fulfill stability via full or half full orbital...

Cr = [Ar]4s13d5 -----> the d subshell is half full and most unpaired electrons...5

 

[Dae204]

oh I get it now. Thank you so much

and I meant Na. sorry

 

[Dmitry Malayev]

Basically anytime in the d subshell you get a 4 or a 9, you take an electron from a s subshell and bring it to the d subshell making it 5 or 10. The atom is much more stable at this state.

I think the Destroyer calls these Pop-Ups.