Download Lecture 9-21-11a

Lecture September 21
Goal for today:
Start Chapter 8 (+ a bit of 7)
Quantum Numbers and
Electronic Structure of Atoms
HW and Quiz 3(2)/7(1) due Monday Sept. 26
Posted an Extra Practice for Naming Compounds
Will post a Practice Exam and a Review
Sheet by Friday evening
CHEM131 - Fall 11 - September 21
1
Quantum Numbers
The quantum numbers from the solution
to the Schrodinger Equation
n, ℓ, and mℓ
n principle q.n. - determines the mean
distance of the electron from the nucleus same as n for the Bohr atom
ℓangular momentum q. n. - shape of the orbital
mℓmagnetic q. n. - orientation in space
CHEM131 - Fall 11 - September 21
2
Rules for the Quantum
Numbers
2
n are whole number integers as in the Bohr atom
mℓ = -ℓ
< n Spectroscopic
notation for ℓ m
ℓ
ℓ
to +ℓ
0
s
0
0
integers
1 p
-1,0,+1
0,1
3
0,1,2
ℓ
n
1
2
d -2,-1,0,+1,+2
3
f
etc.
CHEM131 - Fall 11 - September 21
3
The 1s Orbital
ℓ= 0
See Figures 7.22 - 7.24
CHEM131 - Fall 11 - September 21
4
2s and 3s Orbitals
Figure 7.25
Still a sphere - but
there are NODES in
the internal
distribution
A node is where the
electron probability
density is ZERO
CHEM131 - Fall 11 - September 21
5
More S Orbitals
All s orbitals are spherical mℓ = 0
n=1 no nodes
n=2 1 node
n=3 2 nodes
n=6
H atom
5 nodes
CHEM131 - Fall 11 - September 21
6
p Orbitals
All p orbitals are dumbbell shaped
mℓ = -1, 0, +1
Three orientations px, py, pz
CHEM131 - Fall 11 - September 21
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d Orbitals
Figure 7.27
5 orbitals
f Orbitals
Figure 7.28
7 orbitals
CHEM131 - Fall 11 - September 21
8
Chapter 8 - Multielectron Atoms
Concept of SPIN - electrons have
spin 1/2 and are FERMIONS
New Quantum Number s = 1/2
ms = +1/2 ( spin up ↑) or -1/2 (spin down ↓)
Pauli exclusion principle applies to all FERMIONS
No two electrons in an atom can have the
same 4 quantum numbers
CHEM131 - Fall 11 - September 21
9
Building Atoms
n=1
ℓ
0s
mℓ
0
0
-1,0,+1
ms
± 1/2
# of
electrons
2
n=2
0s
1p
± 1/2
± 1/2
2
6
n=3
0s
0
± 1/2
1p
-1,0,+1
± 1/2
2 d -2,-1,0,+1,+2 ± 1/2
2
6
10
CHEM131 - Fall 11 - September 21
10
Energies of the Orbitals
See Fig. 8.6
Periodic Table follows this energy ordering
H
He
1s1
1s2
B
↑
1s
↑↓ ↑↓
↑↓
1s
1s
Li
Be
1s2 2s1
1s2 2s2
↑↓
↑
1s
2s
↑↓
↑↓
1s
1s2 2s2 2p1
2s
CHEM131 - Fall 11 - September 21
2s
↑
px
Orbital
diagrams
11
Rest of Period 2 (n=2)
C
1s2 2s2 2p2
↑↓ ↑↓
1s
2s
↑ ↑
px py
N 1s2 2s2 2p3
↑↓ ↑↓
1s
2s
↑ ↑ ↑
These are following
Hund’s Rule
the order of filling is
to go in UNPAIRED
first
px py pz
CHEM131 - Fall 11 - September 21
12
Periodic Table and Electron
Configurations
Similar to
Figure
8.8
s and p
electrons
are the
VALENCE
electrons outer
electrons
CHEM131 - Fall 11 - September 21
13
Representative Elements
Filling the s and p orbitals
Electronic configuration of P
1s2 2s2 2p6 3s2 3p3 OR [Ne] 3s2 3p3
Core Notation
Orbital Diagram
↑↓
↑↓
1s
2s
[Ne]
↑↓ ↑↓ ↑↓ ↑↓
2p
3s
↑ ↑ ↑
3p
CHEM131 - Fall 11 - September 21
14
Quiz of the Day
Give the electronic configurations of the
following using the core notation
a) S
b) Mg
[Ne]
2
3s
[Ne]
2
3s
4
3p
CHEM131 - Fall 11 - September 21
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