Period - - -
Orbital Filling and Quantum Numbers
Modified/rom www.gcisd-kI2.org/cms/lihITXOI000829/. ../quantum%20numbers.docandkcntchcmistry.com
Aufbau Principle - electrons fill orbitals starting at the lowest available energy state before filling higher states (ls before 2s).
Pauli Exclusion Principle - An orbital can hold 0, 1, or 2 electrons only, and if there are two electrons in the orbital, they must have opposite (paired) spins. When we draw electrons, we use up and down arrows. So, if an electron is paired up in a box, one arrow is up and the second must be down. Therefore, no two electrons in the same atom can have the same set of four Quantum Numbers. Is 2.s
2.p
[TI] []]] [J][][]
Is 2.s
incorrect; electrons must spin in opposite directions
2.p
IffiJ [IT] ffiJ[][[]. correct;
. .
the electrons have opposite SpinS
-1/2
+1/2
Hund's Rule - When filling sublevels other than s, electrons are placed in individual orbitals before they are paired up. Electrons fill like people do on a bus. You would never sit right next to someone you did not know if there are free seats available, unless of course all the seats are taken then you must pair up. Orbital Filling Questions:
1. Which electron configuration represents a violation of the Pauli Exclusion Principle? 15
A)
2p
2s
15
2p Ii I I
ITTI
~
[IT] [IT] Ii I Ii I
O)ITJ [IJ Ii Ii I i
15
C)
25
[I] Ii ~ I
25
[i]
2p
25
is
t.f ((cA S
2p
2. Which electron configuration represents a violation of Hund's rule for an atom in its ground state?
2s
2p
Is
2s
2p Is
A) [ ]
Is
C)
I
[!lJ
2s
Iii I [!j]
B)
IT]
Is
2p
I
@TI
ITTI Ii I Ii I
[!!] Ii 11 I
2s
2p
3. The correct order of ~ng energy of atomic orbitals is?
..AfSp<4f<6s<5d
~<6S<4f<5d
C) 4f<5p<5d<6s
4.
0) 5p<5d<4f<6s
e orbital diagram in which both Pauli's Exclusion Principle and Hund's rule are violated (2s and 2p orbitals shown):
1i ,1.11 J. 1J. 1J. 1
'---L---L-.JI (0) [ill 1i ~ 1ill i 1
~----,----,I
leI
5. Electr~uld first enter into which orbital?
A) 5s ~
C) 3p
0) 4f
6. Which one ofthe following is the correct electron configuration for a ground-state nitrogen atom?
25
2p Is
25
2p
Is
~
15
C)
Ii 11
IT]
2s
[ill
Iiii Ii I Ii 11 IT!] ~ i Ii Ii I
. IT!] [ill Ii Ii Iii I
Iilli I
B)
15
2p D)
25
2p
fea
Period --
/LG Y
Name
Quantum Numbers
This is our final way to describe the location of an electron. It consists of four numbers that act as coordinates
to locate the electron's position. These numbers will refer only to the element's highest energy electron
because the others fall into the same locations that have been described in the elements preceding it.
1. Prindple Quantum Number (n) is ENERGY LEVEL (SHELL).
o Indicates distance from the nucleus
L _
a. Howdo you determine n? .lroc..-O
Efle.ctj !j {e.ve...{
(,\
pe...r,--aclc-c r~6 ~
01\
b. Possible values of n?
(-7
2. Second Quantum
~umber (ll is the electron SUBSHELL
a. Indicates the shape of the region.
i. Spherical - 5.
LOJ
z
• /y
P LI)
ii. Dumbbell -
' ,. ,
~"
iii. Double dumbbell donut ­
Po
,,
t
-,
/?
..... x
I P,
z
-f (5)
iv. "Fancy" ­
z
y
b. How do you determine I ?
6..=2.
S-=.O
p ~l
~:;:..S
c. f10ssible values of I ?
OJ ( ) 2
J
3
3. Magnetic Quantum Number (mr) is the electron ORBITAL
a. Indicates the orientation of the region in space
L
b. How do you determine
til
mt? - Jef ~ d-s
+eJ ~ -L i-o L LcC4/\.
c. Possible values of
+"'-0.
<Y"'
be
b. {'\
j
o-f'
S
~
:"j
mt ?
fnk9 ~ - [ h
L
4. Spin Quantum Number (ms):
a. When two electrons are in a m"agnetic field, they will align opposite of one another (same as the
up and down arrows). This is called the "spin".
b. The electrons within an orbital must have opposite spins to overcome their repulSion.
c. How do you determine ms
e '/ ~ -er
+- l (
d. Possible values of ms ?
?
~
_ /(
o .{
L
-
c:.
{.J.
(A.
'{IIII1t
1\ \
0-
--t--Ir. e...r Tho ~
- -f-e­
a.. ;--.r k ()..s fz::, h e. Cf~ oS: \
I _l \
r-c--"
r
0
Period -
Name
Quantum Numbers Practice Problems tL:~Y
I
Fill in the orbital notation (arrows) below, then write the four quantum numbers which describe the location of
the highest energy (last) electron of the following elements:
3d
Element
1. Na
-'(1­
2. Ni
or Ift...
- ((L
3. 0
Qr
-YL
4. CI
5. N
c.r
-If 2...
~r- If ~
6. Ar
Give the four quantum numbers which describe the location of each df the following:
7. The 4th electron in carbon
8. The 25 th electron in Mn
.?.) 0 ) 0 ) +YL cr -'I
'2..
3
/
2) c- 2.. to
.) . '\
0))
9. The 57th electron in Ho
'-1)"3 (-3 ~ 3),
10. The 49th electron in Xe
<5/ \) (-l ~ {),J
I
T
1/L
~II
L...
01
or
, ) -t"1(
1..
0 \"
-Ij2..
,- If2­
_II1­
Identify the element whose highest energy electron would have the following four quantum numbers:
" 3 0 ,....._ _
~_ _
A-l_-ro...:...=.._
I
Ac­_ _ _ _ __
11. 33, [)1, -1, + 1/2--,/~'f\~'"J~-fr:..---ll,,-rL.t J.
12. 4, 2, + 1, + 1/2 AC\.~ Lt J 0 \C.- ~ Y
cd
tv
13. Cof.
6, ,0, -1/2.-----=-4_
, A---:-:1+--0-+--f_O-.:;cL._?>
__
T_\ _-6
_~-,----_ _ __
f- +3,
14. '14,3,
/1
u.p
oK ~ Lv-
i-o Y b
-1/2'--'.M--'-1....10~'j,----'L--=-_ _ _ _ _ _-=--_ _ _ __
15. ~,~, + 1, -1/2
I+n 'J 2.-p
0 l?=- ~
B -tv N e...
Which of the following represents a permissible set of quantum numbers? (answer "yes" if permissible and
"no" if no permissible). If no, state why the set won't work.
16.
~,t +1, -1/2 N ~ -==> N 0
17. ~,
t
0,
~
+1/2_yL.....:e~5~--'---_ _ _ _ _ _ _ _ __
Co ~
18. 6,3,-2, +1/2
_
_
I\J ~r/N)....\\ ~ N. 0 1 oS 19. 7,0, 0, -1/2-----<y~e=-=s_ _ _ _ _ ___""__ _ _ _ _ _ _ __ 20.1, if +l/2_--,-N_=o_ _ _(V\~(-",---c_0-_,,_.,_c>_t-__:::;:::..._g­
______