Chem 111
Ch
L t
Lecture
23
UMass- Amherst
6 6 6 Biochemistry
6 6 2 ...Teaching
Initiative
Announcements
• Exam 2 Take Home
Found:
htt //
http://people.chem.umass.edu/cjoseph/chem111/
l h
d / j
h/ h 111/
You may turn it early
Can grab a Scantron
Use any written resource or students in class.
You may NOT use SI's,
Y
SI' Instructors,
I t t
TA's
TA' or ANY OTHER
person outside of class, including "web tutors".
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Homework
• Start Reading Chapter 7
• Owl Homework
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Recap
• Quantum numbers
• Degenerate
D
t
• Spin
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Electron Configuration
ƒ The way in which electrons are distributed among the
various orbitals of an atom is called its electron
configuration.
ƒ The most stable, or ground state, electron configuration
of an atom is that in which the electrons are in the
lowest possible energy state
state.
Hydrogen
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Helium
ƒ Pauli exclusion principle states that no two electrons
in an atom can have the same set of four qauntum
numbers (n, l, ml,, ms)
Helium
ƒ An orbital can hold a maximum of two electrons and
they must have opposite spins
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Effective nuclear charge
ƒ Zeff = Z – σ
ƒ σ : Is
I the
th shielding
hi ldi constant
t t
ns<np<nd<nf
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Lithium
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If you are more math inclined
• Electrons are assigned to
subshells in the order of
increasing “n+ l” value.
• If two subshells with same
n+ l” value electrons are
assigned
g
to the subshell of
lower n.
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Carbon
Hund’s Rule: for degenerate
orbitals, the lowest energy is
attained when the number of
electrons with the same spin is
maximized.
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Let’s Practice
Draw the orbital diagram representation for the electron
configuration of oxygen. What is its electron configuration?
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Magnetism
Paramagnetism: is caused by the presence of at least one
unpaired electron orbital (i.e., an unpaired spin) in the
atoms, molecules, or ions. Attracted to magnets.
Diamagnetism: is caused when all electrons are paired.
Slightly repulsed by magnets.
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Magnetism
Paramagnetism: is caused by the presence of at least one
unpaired electron orbital (i.e., an unpaired spin) in the
atoms, molecules, or ions. Attracted to magnets.
Diamagnetism: is caused when all electrons are paired.
Slightly repulsed by magnets.
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Neon & Sodium
Valence Electrons: the outer shell electrons
Core Electrons: the inner shell electrons
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D-block
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Heavy Elements
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Periodic Table… again
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Let’s Practice
What is the characteristic outer shell electron configuration of
the group 7A elements, the halogens?
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