Subshells and Orbitals
Timberlake LecturePLUS 2000
Quantum Mechanics
Describes the arrangement of electrons
in atoms in terms of:
Main or principal energy levels (n)
Energy subshells
Orbitals (space occupied within the
atom)
Timberlake LecturePLUS 2000
Principal Energy Levels (n)
Contain electrons that are
Close in energy
Similar distance from nucleus
Have values of n = 1, 2, 3, 4, 5, 6…..
Maximum number of electrons = 2n2
n =1
n =2
n=3
2(1)2 = 2
2(2)2 =8
Timberlake LecturePLUS 2000
Energy Levels (Shells)
• A group of electrons in an atom all having the
same principal quantum number (n)
n = 1, 2, 3, …
• The first shell (n = 1) is lowest in energy,
2nd level next and so on 1<2<3<4
• The number of electron in each shell is
limited to 2n2
n=1
n=2
2n2 = 2
2
Timberlake
LecturePLUS
2000
2n
= ____
Energy Levels for Electrons
Some possible electron transitions for the first
three energy levels are shown below. The
negative value means that the electron in the
atom has a lower energy than a free electron
Energy Level
Energy, E
n=3 ___________________ (-) 2.420 x 1019 J
n=2 __________________ (-) 5.445 x 1019 J
18 J
n=1 __________________
(-)
2.178
x
10
Timberlake LecturePLUS 2000
Learning Check S1
A. What energy change (J) takes place when an
electron in a hydrogen atom moves from the
first (n=1) to the second shell (n=2)?
B. What energy change (J) takes place when
the electron moves from the third shell to the
second shell?
Timberlake LecturePLUS 2000
Solution S1
A. What energy change takes place when an
electron in a hydrogen atom moves from the
first (n=1) to the second shell (n=2)?
1.634 x 10-18 J of energy must be absorbed.
B. What energy change takes place when the
electron moves from the third shell to the
second shell?
(-5.445 x 10-19J ) - (2.2420 x 10-19 J) = -3.025 x
1019J will be emitted as electron falls from a
higher to a lower energy state
Timberlake LecturePLUS 2000
Subshells
Energy sublevels within energy level
All electrons in a subshell have the
same energy
Designated s, p, d, f ..
Sublevel energy: s<p<d<f
Timberlake LecturePLUS 2000
Electron Locations
Main
Energy
Levels
n=4
Sublevels
4s, 4p, 4d, 4f
n=3
3s, 3p, 3d
n=2
2s, 2p
n=1
1s
Timberlake LecturePLUS 2000
Sublevels in n = 1,2, 3
n=3
3d
3p
3s
n=2
2p
2s
n=1
1s
Timberlake LecturePLUS 2000
Electrons Allowed
 All electrons in the same sublevel have the same
energy.
 All 2s electrons have the same energy. All 2p
electrons have the same energy which is slightly
higher than the energy of the 2s electrons
s sublevel
2 electrons
p sublevel
6 electrons
d sublevel
10 electrons
f sublevel
14 electrons
Timberlake LecturePLUS 2000
Electron Configuration
 List of subshells containing electrons
 Written in order of increasing energy
 Superscripts give the number of electrons
Example: Electron configuration of neon
number of electrons
1s2
main shell
2s2
2p6
subshell
Timberlake LecturePLUS 2000
Order of Filling
 Total energy of a subshell =
energy of the main shell + the subshell
 The 4s energy < 3d energy
4p
___
3d
___
(finishes the n=3 shell)
4s
___
(starts the n=4 shell)
3p
___
3s
___
2p
___
2s
___
1s
___
Timberlake LecturePLUS 2000
Writing Electron Configurations
H
1s1
He
1s2
Li
1s2
2s1
C
1s2
2s2
2p2
S
1s2
2s2
2p6
3s2
Timberlake LecturePLUS 2000
3p4
Sublevel Blocks
s1 s2
1
2
3
4
5
6
p1 p2 p3 p4 p5 p6
d1 - d10
f1 - f14
Timberlake LecturePLUS 2000
Periodic Table and Electron
Configuration
Find the element on the periodic
table
Use the order of filling indicated
across each period
Groups 1-2
= s level
Groups 3-8
= p level
Transition
= d level
Lantanides
= f level
Timberlake LecturePLUS 2000
Learning Check S2
Indicate if each configuration is (1) correct or
(2) incorrect for potassium. Give an
explanation for selection of 1 or 2. Explain
why or why not?
A.
1s22s22p63s1
1 or 2
B.
1s22s22p63s23p6
1 or 2
C.
1s22s22p63s23p64s1
1 or 2
D.
1s22p83s1
1 or 2
E.
63s23p7
1s22s22p
Timberlake LecturePLUS 2000
1 or 2
Solution E2
For phosphorus, indicate if each
configuration is (1) correct or (2) incorrect.
Explain why or why not.
A. 2, 2, 8, 5
2
B. 2, 8, 3
2
C. 2, 8, 5
1
D. 2, 6, 7
2
Timberlake LecturePLUS 2000
Learning Check S3
Using the periodic table, write the complete
electronic configuration for each:
A. Cl
B. Sr
C. I
Timberlake LecturePLUS 2000
Solution S3
Using the periodic table, write the complete
electronic configuration for each:
A. Cl
1s2 2s2 2p6 3s2 3p5
B. Sr
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
C. I
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5
Timberlake LecturePLUS 2000
Learning Check S4
A.
The final two notations for Co are
1) 3p64s2
2) 4s24d7
3) 4s23d7
B. The final three notations for Sn are
1) 5s25p24d10
2) 5s24d105p2
3) 5s25d105p2
Timberlake LecturePLUS 2000
Solution S4
A.
The final two notations for Co are
3) 4s2 3d7
B. The final three notations for Sn are
2) 5s2 4d10 5p2
Timberlake LecturePLUS 2000
Orbital
 A 3 dimensional space around a nucleus in
which electrons are most likely to be found
 Shape represents electron density (not a
path the electron follows)
 Each orbital can hold up to 2 electrons.
Timberlake LecturePLUS 2000
s orbitals
1s
2s
Timberlake LecturePLUS 2000
3s
Three p Orbitals
px
pz
Timberlake LecturePLUS 2000
py
p subshell contains p orbitals
Timberlake LecturePLUS 2000
d orbitals
Timberlake LecturePLUS 2000
Learning Check S5
A. Number of electrons in a p orbital
1) 1e
2) 1e or 2e 3) 3e
B. Number of orbitals in a p subshell
1) 1
2) 2
3) 3
C. Number of orbitals in 4d subshell
1) 1
2) 3
3) 5
D. Number of electrons (maximum) in a 3d
subshell
1) 2e
2) 5e
3) 10e
Timberlake LecturePLUS 2000
Solution S5
A. Number of electrons in a p orbital
2) 1e or 2e
B. Number of orbitals in a p subshell
3) 3
C. Number of orbitals in 4d subshell
3) 5
D. Number of electrons in a 3d subshell
3) 10e
Timberlake LecturePLUS 2000