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

0

1.67492716 x10-24

What makes an element an element?

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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 questionsWhy is the actual mass of 12C lower than the

mass of all of its subatomic particles?

Picture from: www.utwente.nl/wyp/einstein/

When neutrons and protons are bound together in the nucleus, the energy of the system is lowered.

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 12C12.1119 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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• 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

C60

“Buckyball”C70

Four Allotropes of CarbonM

IrReSPONSiBILiTiEs is the longest word that can be spelled entirely using chemical symbols without reusing any element...

Ir - iridiumRe - rheniumS - sulphurP - phosphorusO - oxygenN - nitrogenSi - siliconBi - bismuthLi - lithiumTi - titaniumEs – 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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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

H 1 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 Au 197?

C 12 Si 28 ? 70 Sn 118

N 14 P 31 As 75 Sb 122 Bi 210?

O 16 S 32 Se 79.4 Te 128?

F 19 Cl 35.5 Br 80 I 127

Li 7 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

In 75.6? Th 118?

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Mendeleev's 1871 Periodic Table….

R2O RO R2O3

RH4

RO2

RH3

R2O3

RH2

RO3

RH

R2O7 RO4

H 1

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 Fe, Co, Ni, Cu 56, 59, 59, 63

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 Ru, Rh, Pd, Ag 104, 104, 106, 108

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 Os, Ir, Pt, Au, 195,197,198,199

? Au 199

Hg 200 Tl 204 Pb 207 Bi 208 ? ?

? ? ? Th 231 ? U 240 ?

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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 reactionsThe 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) 1s22s22p63s23p64s23d104p65s24d2

b) 1s22s22p63s43p64s23d104p65s24d2

c) 1s22s22p63s23p64s23d104p65s25d2

d) 1s22s22p63s23p64s23d104p64d4

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Order = n + lwith preference given to lowest value of n.

Quantum numbers n and l discussed in studio 3a “The Atomic Hotel”

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s block

p blockd block

f block

What do all of the Group 1 Elements have in common?

How would you describe “the” periodic table in relationship to electron configuration; particularly to valence electrons?

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H 1s1

Li 1s22s1

Na [Ne] 3s1

K [Ar] 4s1

Rb [Kr] 5s1

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

Images from: www.vetref.net/ emscope/theorysch.html

1930s

Image ~12 atom molecule

Must be used under vacuum

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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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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.

STM (Scanning Tunneling Microscope)

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STM2. 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

http://www.almaden.ibm.com/vis/stm/atomo.html

copper

nickel

The Kanji characters for "atom." The literal translation is something like "original child."

iron on copper

Surface must be an electrical conductor

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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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• 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.

How It WorksM

Heinz, William F.; Hoh, Jan H. J. Chem. Educ. 2005 82 695.

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http://www.inkyfingers.com/RECORD/CECILEX/Cecil7.html

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.

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Image obtained from Digital Instruments website: http://www.di.com/NanoTheatre/theater.html

CD-R

Surface Characterization

TappingModeTM AFM image of disc surface10µm x 10 µm

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-16 min.

16 min.

48 min.

1 hr 20 min.

1 hr 52 min.

2 hrs 24 min.

Distance (µm)

Hei

ght

(µm

)

1500

2000

2500

3000

3500

0 20 40 60 80 100 120 140

Time (min.)

Vol

um

e (u

m3 )

Using AFM to Studio Programmed Cell Death (Apoptosis)

J. Hessler et al. Langmuir 2005, 21, 9280-9286.

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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.

More AFM ImagesM

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 1-1000 nm size scale.

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He was booked for a salt and battery.

What happened to the man who was stopped for having sodium chloride and a nine-volt in his car?

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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

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