gchem quantum # question...

[hoss19]

ive been studyig up on gchem getting ready to take a practive Dat this saturday and one question is driving me CRAZY (from my text)!

"what is the maximum # of electrons in an atom whose highest-energy electrons have the principal quantum number n = 5?"

my answer would have been 113 - [Rn] 7s2 5f14 6d1, considering that the electrons are in the 5f subshell (which is maximized, ie full)

the answer is 138 (obviously theortetical). the answer claims that there is a 5g orbital and the 138 is calculate by [Rn] 7s2 5f14 6d10 7p6 5g18

Can anybody explain?

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[klutzy1987]

i agree with you and i never heard of a G orbital either

 

[bigstix808]

shoot, i would have put 110

max # of e- per energy level = 2n^2

so i got 2+8+18+32+50=110

edit: i don't think you'll get some kind of theory question like that, but if you'd like you can try to makes heads or tails of this

 

[gomawum]

2n^2 = 2*(5)^2 = 100 isn't it?

and I tried to reason it

n = 5
l = 0, 1, 2, 3, 4
ml = 1 for o
3 for 1
5 for 2
7 for 3
9 for 4

so there are total 25 orbitals exist according to ml,
and mutiply 25 by 2 because each oritals can have 2 e-
so I got 100..

but.. where is 138 from? ???

 

[A8]

My apology it is # of electrons in an atom, not just for n=5 so it becomes 2(1+2^2+3^2+4^2+5^2)=2(55)=110! but still not 138!!

 

[bigstix808]

I use 2(n^2)=2(5^2)=100 so I think the answer is 100! I don't understand why 138!!

AND

2n^2 = 2*(5)^2 = 100 isn't it?

and I tried to reason it

n = 5
l = 0, 1, 2, 3, 4
ml = 1 for o
3 for 1
5 for 2
7 for 3
9 for 4

so there are total 25 orbitals exist according to ml,
and mutiply 25 by 2 because each oritals can have 2 e-
so I got 100..

but.. where is 138 from? ???

i'm not sure what either one of you were thinking...but you're going to have bigger problems if you can't remember the simple order of operations...2(5^2)=50 NOT 100 "Please Excuse My Dear Aunt Sally" -- ring a bell????

2(5^2)=2(25)=50

oh, just something else to keep you from messing up later on, you use 2n^2 for the max number of e- PER ENERGY LEVEL - not total. so it would really be
2(1^2) + 2(2^2) + 2(3^2) + 2(4^2) + 2(5^2) = 110

 

[klutzy1987]

i askd about it and supposedly there is a g orbital that has 9 subshells and can hold 18 electrons. We have never actually discovered the g orbital and it exists only in theory. You dont need to go to that depth for the DAT though so you are ok even if you do not know about these orbitals. I for one didnt.

 

[hoss19]

i askd about it and supposedly there is a g orbital that has 9 subshells and can hold 18 electrons. We have never actually discovered the g orbital and it exists only in theory. You dont need to go to that depth for the DAT though so you are ok even if you do not know about these orbitals. I for one didnt.

thanks!!