Chem 111
Ch
L t
Lecture
26
6
UMass- Amherst
6 6 6 Biochemistry
6 6 2 ...Teaching
Initiative
Announcement
• Recitation session, Wednesday 11/17 at HASA 126 (5-6pm)
• The
Th Exam,
E
d t
data
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Homework
• Finish Reading Chapter 7
• Owl Homework
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Recap
• Magnetism
• Valence
V l
El
Electrons
t
vs Core
C
El
Electrons
t
• D-block
• Periodic Table
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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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Atomic Radii
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Ionization energy
ƒ Ease in which an electron can be removed
ƒ A(g) ÆA+(g) + e-(g)
Na(g) ÆNa+(g) + e-(g)
ƒ I = E(A+) – E(A)
ƒ First Ionization Energy, I1
ƒ Second Ionization, I2
Na+(g) ÆNa2+(g) + e-(g)
I1 < I2 < I3
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Electron Configuration of Ions
ƒ Sodium
N [1
Na:
[1s22s
2 22p
2 63s
3 1] Æ Na
N +: [1s
[1 22s
2 22p
2 6] + eƒ Germanium
Ge: [Ar]3d104s24p2 Æ Ge2+:[Ar]3d104s2 + 2eƒ Iron
Fe: [Ar]3d64s2 Æ Fe2+:[Ar]3d6 + 2eFe: [Ar]3d64s2 Æ Fe3+:[Ar]3d5 + 3e-
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Ionization energy
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Electron affinity
ƒ Ease in which an electron can be added
ƒ A(g) + e- (g) Æ A- (g)
Cl(g) + e- (g) Æ Cl- (g)
ƒ Ea = E(A) – E(A- )
ƒ The more negative Ea the easier it is to put an electron on to
the atom.
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Electron affinity
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Summary of Trends
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Trends in Ions Sizes
If an atom loses electrons, the resulting cation will be smaller
in size than the parent atom.
If an atom gains electrons,
electrons the resulting anion will be larger in
size than the parent atom.
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Let’s Practice
Which will be closer to the nucleus, the n= 3 electron shell in Ar
or the n=3 shell in Kr?
Arrange the following atoms in order of increasing first
ionization energy: Ne, Na, P, Ar, K.
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Bonding
Ionic Bonds – refers to electrostatic forces that exist between
ions of opposite charge.
Covalent Bonds – results from the sharing of electrons
between two or more atoms.
The electron involved in bonding are the valance electrons.
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Lewis Structure
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Covalent Bond
Non metals (hydrogen & P-Block)
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Octet
Each atom wants to fill its valence electron shell (have a noble
gas configuration). Lewis structures will want (mostly) want an
octet
t t (8) electrons
l t
around
d an atom.
t
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