Help with a chem question

[CpharmAH1]

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How many unpaired electrons are there for the element whose atomic number is 23?

a) 1

b) 3

c) 5

d) 7

I don't get the right answer I want to check with you guys to see if it's mistake, or i'm doing it wrong.thanks.😉

 

[nerv12345]

is the answer C? 3 unpaired electrons?

 

[CpharmAH1]

yes, its 3, how is it?

 

[nerv12345]

i just used the aufbau principle

1s
2s 2p
3s 3p 3d
4s 4p
5s

1s,2s,2p,3s,3p,4s,3d

since 1s --> 4s = 20 electrons, there's only 3 left for 3d

3d would be:

| | | __ __ __

edit: i'm such an idiot...i meant B (3 unpaired electrons) not C haha.

 

[CpharmAH1]

ok. thanks for your help.

 

[Knickerbocker]

Aufbau's as nerv12345 said, plus Hund's rule.

I don't ever draw it out like that for electron configuration, I find it easier to just use the shape of the periodic table. Unfortunately, you wouldn't have a periodic table for the test.

 

[sASU]

so its 3 unpaired electrons and not 7 electrons left to fill out 3d. Thats kinda tricky I guess.

 

[nerv12345]

it's not asking you how many are needed to be filled it's asking you how many UNPAIRED electrons are there

 

[sASU]

it's not asking you how many are needed to be filled it's asking you how many UNPAIRED electrons are there

Ya I got you, but for some reason I though 7 since thats how many were left to fill it out. I need to read stuff more carefully.