Romantic Atomic Love Affairs?
http://www.youtube.com/wat
ch?v=6nclUZoouHQ
http://www.youtube.co
m/watch?v=L4w1Mp6Mc
e4&feature=related
Trivia: besides LSU, what university sings
Hey Baby at games?
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Love isn’t always romantic.
Hotel Californian—Santa Barbara
http://www.edhat.com/img2/beats/HC-006.jpg
Atomic dating is more often needy, fast and brutal,
the surroundings messy and cheap.
Electrons exist in orbitals. We can think of these as
Bohrbits…Standing Waves in 3 Dimensions.
Of course 2-D is easier to see.
Sand on a kettle drum!
By this analogy, electrons
would be where sand isn’t
(sand sits at the nodes).
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Bohrbits: More energy  can afford more complexity.
These are standing waves in three dimensions.
http://chemlinks.beloit.edu/Stars/images/orbitals.jpg
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Crayola Periodic Table
1s
2s
3s
4s
2p
3p
4p
3d
Coulomb's Law: opposites attract.
 
q q
F 2
r
F
-
Slow, low-E electron
Small radius
-
+
Big radius
Fast, high-E electron
+
Electron Configurations: how are electrons
partitioned according to energy?
Example:
Calcium = 1s22s22p63s23p64s2
There are all kinds of mnemonic devices for
this (see your textbook, and also the notes
or
) but the easy solution is:
Just follow the periodic table!
But first a romantic (?) Southern riddle about
Billy Joe and Annabelle Leigh*
*With apologies to Edgar Allen Poe
Mendeleev was even able to predict!
One example: Eka-silicon (Ge)
At.Wt.
Color
Density
Predicted 1871
72
gray
5.5
Discovered 1886
72.6
gray
5.5
(g/cm3)
Oxide
Chloride
B.P. Chloride
(oC)
EsO2
EsCl4
Under 100
GeO2
GeCl4
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Meyer also saw periodicity. His version was
physical—we can imagine it was size-based.
But how do we know this???
Other things that repeat
•Density
•Boiling point
•Melting point
•Ionization energy (e.g., how
hard to yank an electron away)
•Which way do you think
ionization energy goes?
It is hard to steal electrons from the elements
on the right side of the periodic table.
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Electronegativity
•Define: the "desire" an atom has for electrons
•All atoms desire electrons—a matter of degree
•Atoms at the very right of the table (with completely full shells)
don't want to acquire more electrons.
•Atoms near the right of the periodic table (with almost full shells)
want electrons very badly. We say these atoms (like chlorine or
fluorine) are electronegative.
•Atoms on the left are glad (well, not too sad) to give them up.
1. The most electronegative atom is F.
2. Electronegativity is yet another thing that repeats.
Major groups: most elements are metals!
Group VIII are the Noble Gases
•Too regal to react
•All end in s2p6 ***
•Example: Argon =
1s22s22p63s23p6
***Except He (1s2)
“We are not amused.”
Group I and Group II = Metals
Alkali metals, example Sodium
not greedy at all—ready to lose
electrons—its last electron was
high-energy and “out there”
ready to get stolen!
Na = 1s22s22p63s1
Mg = 1s22s22p63s2
Group VII = Halides
Example: Chlorine
very greedy:
Chlorine: 1s22s22p63s23p5
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Transition metals: electrons galore, but not
desperate to get rid of them—lots of protons to
hold electrons where they are.
example Iron:
--Sea of electrons
--certainly enough electrons to conduct electricity
--but not desperate to get rid of them
Fe: 1s22s22p63s23p64s23d6
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Nonmetals
example Carbon: share and share alike
C: 1s22s22p2
Si: 1s22s22p63s23p2
Metalloids
example Silicon: can be
"doped" to behave a little bit like metals;
semiconductors
http://1.bp.blogspot.com/_Zx0SO3YqO2g/TCGo5P6JawI/AAAAAAAAAA8/sdLBzI2Fep4/s320/Transistor.jpg
Octet Rule: Chemistry often follows the
rule of 8’s: Atoms try to end in s2p6
•Rule of 8's: the s2p6 configuration is very stable:
noble gases
•Atomic jealousy: every atom wants to look like
s2p6--e.g., Na  Na+1
•Why?---What is special about s2p6?
Is there an easy answer?
Who is more likely to encounter extraterrestrial life, you or one of these people?
We repeat: electrons that are “out there”
are more energetic…and more likely to be
found by other atoms.
-
Slow, low-E electron
+
-
Fast, high-E electron
+
Valence Electrons = Energetic, Outer Electrons
The active electrons are called valence electrons.
Inner shell electrons are “screened”—not so visible to
alien atoms.
Examples:
Potassium has 19 electrons,
but only 1 valence electron
Carbon has 12 electrons,
but only 4 valence electrons
The number of valence electrons = the Group Number!
Lewis Dot Structures
show just the valence electrons
By Octet rule, Chorine would rather be
this anion:
-1
Preview
Cl2, O2, N2 examples
Na & Br example
Don’t worry, we’ll get LOTS
more covalent examples later!
Coulomb's Law: Can we explain Meyer’s size
trends, ionization energies & electronegativity?
 
F
Compare Cl and Na
Cl has q+ = 17
Na has q+ = 11
q q
F 2
r
Cl pulls harder on its electrons
than Na. So….Cl will steal from
Na…and put the electron in
a smaller orbital, too,
closer to nucleus.
See? Cl is smaller. And Ar is smaller still.
Then why does K get bigger again?
More energy! K’s last electron has energy
quantum number n=4
The last electron captured by the K
nucleus was a fast, energetic one.
The last electron placed determines what
the atom wants to do.
Types of Bonds: Quick Intro
Ionic Bonds: back to the legend
of Billy and Annabelle Leigh
Define: An ion is an atom or molecule that
carries a net charge.
Cation = + ion (lost an electron)
Anion = - ion (gained an electron)
Anions attract Cations
Billy Joe pulls a wig out of his pocket, gives to
Annabelle Leigh. Then they can snuggle.
Billy Joe Cation
Annabelle Leigh Anion
Why do ions form?
Ions form generally because atoms
.
Na 
+
Na
+
e
Note balance of charge!
No charge on left side of arrow.
None on right.
Why do ions form?
Ions form generally because atoms
.
Cl +
e-

Cl
Note balance of charge!
-1 charge on left side of arrow.
-1 on right.
The public debt of the U.S. is calculated
to the penny!
March 1, 2005: $7,701,629,503,518.55
October 5, 2011: $14,837,099,271,196.71
Your share: about $47,400
It goes up by about $13/day/person
http://www.usdebtclock.org/
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Electrons & Protons do an even better
balancing act. Balance to better than…
1 : 1,000,000,000,000,000,000,000,000
+
+
Fcoulombic for 1% imbalance of charges
would lift Earth in its own gravity
(from Feynman Lectures)
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Isoelectronic =
Same Electronic Configuration
Ne /
+
Na
/
++
Mg
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A Note About Notation
Mg++ means the same thing as Mg2+
Either is very different from something like Mg2+
(not a normal form of magnesium)
DOWN (SUBSCRIPTS) = how many atoms
UP (SUPERSCRIPTS) = how many charges
48
Left subs/supers vs.
Right subs/supers
protons
+
neutrons 22
protons
electronic
charge
1
2 how many
Na
11
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Oxidation means losing electrons.
We have seen cases where atoms give up electrons
to form cations.
This is an example of oxidation.
Where do such electrons go?
Reduction:
gaining electrons
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Example: chloride anion
Consider the case where chlorine
gets reduced (gains an electron)
Cl = 1s2 2s2 2p6 3s2 3p5
Cl + e-  Cl-
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Let’s do another, more highly
charged, anion
N = 1s2 2s2 2p3
Let it gain three electrons to become
nitride:
52
Suppose we repeat with Mg and F
Mg  Mg2+ + 2e2e- + 2F  2FMg + 2F  MgF2
It takes TWO Fluorines to soak up the
TWO electrons from the ONE magnesium.
Uh-oh….Here is our first atomic “three-way.”
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One oxygen could serve same "soakup"
function as 2 fluorides.
Mg  Mg2+ + 2e2e- + O  O2_____________________________________
Mg + O  MgO
Magnesium Oxide
55
Let’s do Na and N
Let’s do Ca and N
56
Na and N answer
3 Na  3Na+ + 3e3e- + N  N3______________________________________
3Na + N  Na3N
Sodium nitride
57
Ca and N answer
Ca  Ca2+ + 2e3e- + N  N3Doesn't balance!
Multiply top by 3 and bottom by 2
3 Ca  3Ca+2 + 6e6e- + 2N  2 N3___________________________________________
3Ca + 2 N  Ca3 N2
Calcium nitride
58
Here’s a trick for predicting ionic compounds from
the periodic table (Life and Chemistry are both full of tricks!)
•Count how many electrons the metal must lose to
become like a rare gas. (2 for calcium).
•Give this number to the nonmetal.
•Count how many electrons the nonmetal must gain to
•become like a rare gas. (3 for nitrogen)
•Give this number to the metal.
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What do Si and O make?
What do Al and O make?
What do Fe and O make?
(uh-oh)
60
Breaking Ionic Bonds…
…..can be as simple as adding water
NaCl  Na+ + ClH2O
Sometimes, it is much harder….
e.g., Al2O3
61
Covalent Bonding is The Gray
Area of Electron Accounting
Not everything is black and white like the all or nothing electron
transfer of ionic bonds.
Ionic bonds can't explain molecules like Cl2.
Both atoms in a Cl2 molecule want the electrons equally.
....But the octet rule still can!
62
Think of atoms like people:
Ionic People Matching Set
Oxygen, Fluorine
Potassium, Cesium
63
Covalent People
Silicon
Carbon
64
http://media.photobucket.com/image/fat%20cat/misscole1o1/Internet%2520Pictures/FatCat.jpg
http://www.funnyanimalpictures.net/data/media/1/skinny-cat-dance.gif
65
Sample Covalent Bonding
66
Let’s do oxygen, O2
67
Oxygen Answer
68
2 covalent electrons
in
one orbital = 1 covalent bond
69
Do Nitrogen, N2
70
Q. Are we ready for complex covalent molecules yet?
A. Almost.
Astaxanthin, a member of the
carotenoid family, is part of a nutritious
diet—for lobsters and shrimp. These
crustaceans bind astaxanthin to the protein
β-crustacyanin, which changes the shape of
the astaxanthin molecules, turning them a
gray-blue color. Cooking releases the
molecules, returning them to their original
bright red color.
cook
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