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Intersection 3
Reading: 1.4 p 6-11; 2.3-2.4 p 44-52;
2.9 p 62-68
[http://www.chemsoc.org/viselements/pages/history.html
(history of the periodic table)]
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News bit: Forensic Chemistry
Isotopes:
– Corn syrup and grape juice have the same
sugar, but different 12C:13C ratio
– 18O:16 O in one’s hair can determine one’s
hometown (bottled water and dye don’t matter)
– DEA pinpoints narcotic sources
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Outline
• Elements and atoms
• “The” periodic table
• Seeing atoms today
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Elements __________ Atoms
Subatomic
particle
Mass (g)
Charge
9.10938188 x10-28
1.6762158 x10-24
1.67492716 x10-24
What makes an element an element?
0
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Why were our masses higher than
those on the periodic table?
12C
98.89%
__ neutrons 1.6762158 x10-24 g
__ protons 1.67492716 x10-24 g
__ electrons 9.10938188 x10-28 g
1 amu = 1.66054 x10-24g
Find the mass of a 12C atom in amu:
Actual mass of 12C = 12.000000 amu
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More questions
Why is the actual mass of 12C lower than the
mass of all of its subatomic particles?
When neutrons and protons are bound
together in the nucleus, the energy of the
system is lowered.
Picture from:
www.utwente.nl/wyp/einstein/
Energy (heat or light) is given off. This
energy comes from the mass (E = mc2)
resulting in a net mass loss.
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Nuclear binding energy: the energy required to break a nucleus
into its individual protons and neutrons.
For 12C
12.1119 amu – 12.0000 amu = 0.1119 amu
0.1119 amu * 931.494 MeV = 104.3 MeV = 1.678x10-11 J
amu
For a mole (12 grams) of 12C = 1.010 x 1013 J
1J
potential energy of a small apple (102g; 4.67 moles of
molecules) 1m above the surface of the earth
4.184 x1012 J
energy released by explosion of 1 kiloton (4x106 moles) of
TNT
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Concept Question 1
Antoine Lavoisier, the "father of chemistry", listed lime
as a chemical element in his table of 33 known
elements. Which of the following observations best
shows that lime cannot be an element?
(a) Lime reacts with water, generating a large amount of
heat.
(b) Lime and carbon dioxide are produced when limestone is
roasted.
(c) When a certain soft metal is burned in oxygen, lime is
produced (with no other products).
(d) Lime melts at a temperature of 2572°C.
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Elements
• Modern definition:An element is in this definition 'matter,
all of whose atoms are alike in having the same positive
charge on the nucleus.' Or, having the same number of
protons in the nucleus.
• The diatomic elements:
– H, O, N, and the halogens (H2, O2, N2, F2, Cl2, Br2, I2)
• Allotropes are different forms of the same element in the
same physical state at the same temperature and pressure.
– O2 vs. O3
– diamond, graphite, C60 buckyballs
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Four Allotropes of Carbon
C60
“Buckyball”
•
•
•
C70
http://www.bris.ac.uk/Depts/Chemistry/MOTM/diamond/diamond.htm
http://www.chem.yorku.ca/hall_of_fame/essays98/buckyball/bucky1/bucky.htm
flex.ee.uec.ac.jp/ ~naka/fulleren.html
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IrReSPONSiBILiTiEs is the longest word that
can be spelled entirely using chemical
symbols without reusing any element...
Ir - iridium
Re - rhenium
S - sulphur
P - phosphorus
O - oxygen
N - nitrogen
Si - silicon
Bi - bismuth
Li - lithium
Ti - titanium
Es – einsteinium
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How do you go from elements to the
periodic table?
Mendeleev's 1869 Periodic Table….
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• Animation File
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H1
Li 7
Ti 50
Zr 90
? 100
V 51
Nb 94
Ta 182
Cr 52
Mo 96
W 186
Mn 55
Rh 104.4
Pt 197.4
Fe 56
Ru 104.4
Ir 198
Ni, Co 59
Pd 106.6
Os 199
Cu 63.4
Ag 108
Hg 200
Be 9.4
Mg 24
Zn 65.2
Cd 112
B 11
Al 27.4
? 68
U 116
C 12
Si 28
? 70
Sn 118
N 14
P 31
As 75
Sb 122
O 16
S 32
Se 79.4
Te 128?
F 19
Cl 35.5
Br 80
I 127
Na 23
K 39
Rb 85.4
Cs 133
Tl 204
Ca 40
Sr 87.6
Ba 137
Pb 207
? 45
Ce 92
Er? 56
La 94
Yt? 60
Di 95
Au 197?
Bi 210?
AMendeleev's 1871 Periodic Table….
R2O
RO
RH4
RO2
R2O3
RH3
R2O3
RH2
RO3
RH
R2O7
RO4
H1
Li 7
Be 9.4
B 11
C 12
N 14
O 16
F 19
Na 23
Mg 24
Al 27.3
Si 28
P 31
S 32
Cl 35.5
K 39
Ca 40
? 44
Ti 48
V 51
Cr 52
Mn 55
Cu 63
Zn 65
? 68
? 72
As 75
Se 78
Br 80
Rb 85
Sr 87
? Yt 88
Zr 90
Nb 94
Mo 96
? 100
Ag 108
Cd 112
In 113
Sn 118
Sb 122
Te 125
I 127
Cs 133
Ba 137
? Di 138
? Ce 140
?
?
?
?,?,?,?
?
?
?
?
?
?
?
?
?
?
?Er 178
??La 180
Ta 182
W 184
? Au
199
Hg 200
Tl 204
Pb 207
Bi 208
?
?
?
?
?
Th 231
?
U 240
?
Fe, Co, Ni, Cu
56, 59, 59, 63
Ru, Rh, Pd, Ag
104, 104, 106, 108
Os, Ir, Pt, Au,
195,197,198,199
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How can you organize the elements?
• Observe the appearance, malleability, and
reactivity of:
–
–
–
–
–
–
–
aluminum
beryllium
calcium
lithium
magnesium
potassium
sodium
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Two Columns (Groups) of Elements
Describe any trends you observed in groups 1
and 2.
• Rb and Cs are in the same column as Li,
Na, and K on both the modern periodic
table and Mendeleev's. What properties do
you think that they have? Ask Ed if he will
show you what happens when Rb and Cs
are mixed with water.
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Writing chemical reactions
The reaction between lithium and water forms a
lithium hydroxide and hydrogen gas. The
reaction gives off so much heat that it can
ignite the hydrogen gas.
Name
Symbol
State
lithium
water
lithium hydroxide
hydrogen
____Li(s) + ____H2O(l)
____LiOH(aq)
+ ____H2(g)
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Group 1
• Write balanced chemical equations for the
reaction of sodium and potassium with
water.
• How do other metals such as copper and
silver compare to the group 1 metals in
physical properites and reactivity with
water?
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Group 2
• What distinguishes the group 1 and group 2
metals?
• Group 2 metals form hydroxides in a ratio
of 1:2 that have chemical formula such as
Mg(OH)2. Write balanced chemical
equations for the reaction of the group two
metals with water.
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Rows (Periods)
• Describe how elements in rows are related.
• Na, Mg, and Al are all in the same row.
Predict the physical properties and
reactivity of aluminum.
• Are elements in groups or periods more
alike?
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Concept Question 2
Which is the correct electron configuration for Zr?
a)
b)
c)
d)
1s22s22p63s23p64s23d104p65s24d2
1s22s22p63s43p64s23d104p65s24d2
1s22s22p63s23p64s23d104p65s25d2
1s22s22p63s23p64s23d104p64d4
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Order = n + l
with preference given
to lowest value of n.
Quantum numbers n
and l discussed in
studio 3a “The
Atomic Hotel”
s block
d block
p block
f block
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What do all of the Group 1 Elements
have in common?
H
1s1
Li
1s22s1
Na [Ne] 3s1
K [Ar] 4s1
Rb [Kr] 5s1
How would you describe “the”
periodic table in relationship to
electron configuration;
particularly to valence
electrons?
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Is there a single way to organize the
elements?
• In this song (Visual version)
• What are some ways in which the elements
were grouped?
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Other Periodic
Tables
How is this table
organized?
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The Periodic Spiral of
Professor Thoedor Benfey
From The Pictorial Periodic Table by Chris Heilman
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Tarantola
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Seeing Atoms Today
http://www.almaden.ibm.com/vis/stm/stm.html
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Electron
Microscope
1930s
Image ~12 atom
molecule
Must be used under
vacuum
Images from: www.vetref.net/ emscope/theorysch.html
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SEM Images
Images from: www2.ijs.si/~goran/ semmate2.html
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STM (Scanning Tunneling
Microscope) 1983
STM 1986 Nobel Laureates Heinrich
Rohrer and Gerd Binnig
http://nobelprize.org/physics/educational/microscopes/scanning/
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STM (Scanning Tunneling
Microscope)
1. A tip is scanned over a surface
at a distance of a few atomic
diameters in a point-by-point
and line-by-line fashion. At
each point the tunneling current
between the tip and the surface
is measured. The tunneling
current decreases exponentially
with increasing distance and
thus, through the use of a
feedback loop, the vertical
position of the tip can be
adjusted to a constant distance
from the surface.
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STM
2. The amount of these adjustments is recorded and defines a grid of
values which can be displayed as a grayscale image.
3. Instead of assigning the values to a color we can also use them to
deform the grid in the direction perpendicular to the surface.
4. Now we can bring back the grayscale and paint each square according
to an average of the four defining grid points.
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STM images of elements and atoms
Surface must be an electrical conductor
nickel
iron on copper
copper
http://www.almaden.ibm.com/vis/stm/atomo.html
The Kanji characters for "atom."
The literal translation is
something like "original child."
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Macro models nano
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•1985
•Technique can directly resolve
nanoscale features: 0.2nm in Z,
1-2nm in X, Y.
• Can function in air and in
fluids.
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How It Works
• Laser beam is reflected off the back of the
cantilever as it is raster scanned across the
surface.
• When tip encounters a feature on the surface,
displacement of the cantilever results in
displacement of the laser beam on the detector.
• For example, if the tip scans across a feature
projecting from the sample surface, the
cantilever will deflect upwards and the
resultant laser spot on the detector will be
displaced lower.
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Heinz, William F.; Hoh, Jan H. J. Chem. Educ. 2005 82 695.
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Basic Mode 1: Contact Mode
• In contact mode, the tip is
constantly in touch with the
sample surface.
• Similar to a record player,
the sample is moved
underneath the tip.
• The tip reads the “bumps and
grooves” in the sample
surface, only instead of
converting these bumps and
grooves into music, the AFM
converts them into a
topographic image.
http://www.inkyfingers.com/RECORD/CECILEX/Cecil7.html
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Surface Characterization
CD-R
TappingModeTM AFM image of disc surface
10µm x 10 µm
Image obtained from Digital Instruments website: http://www.di.com/NanoTheatre/theater.html
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Using AFM to Studio Programmed
Cell Death (Apoptosis)
-16 min.
Height (µm)
16 min.
Volume (um3)
3500
3000
48 min.
1 hr 20 min.
1 hr 52 min.
2 hrs 24 min.
2500
2000
Distance (µm)
1500
0
20
40
60
80
100
120
140
Time (min.)
J. Hessler et al. Langmuir 2005, 21, 9280-9286.
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More AFM Images
Zhao,Y.; Chen, Z.; Yuan,H.; Gao, X.; Qu, L.; Chai, Z.; Xing, G.; Yoshimoto, S.;
Tsutsumi, F.; Itaya, K. “Highly Selective and Simple Synthesis of C2m-X-C2n
Fullerene Dimers” J.Am. Chem. Soc. 2004, 126, 11134 – 11135.
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Seeing Atoms Today
Scanning Probe Microscopes (STM and
AFM) allow us to explore chemistry at
an atom by atom level as well as in the 11000 nm size scale.
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What happened to the man who was
stopped for having sodium chloride
and a nine-volt in his car?
He was booked for a salt and battery.
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Concept Question 3
What is the approximate number of carbon
atoms it would take placed next to each other
to make a line that would cross this dot: •
a. 4
b.200
c. 30,000,000
d.6.02 x 1023
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First Group Assignment Food Brief
Studio, Friday 9/29/06
Topics:
Trans fats; MSG; Nitrates; homogenization
of milk; Vitamin D in OJ; Fluoride;
Fortified flour; iodized salt
Tie in chemistry and a scientific study
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Other Reminders
• Penny report due 9/22
• HW 3 Due 9/25