For copyright notice see final page of this file Chemistry 125: Lecture 4 Coping with Earnshaw, Smallness and Scanning Probe Microscopy Despite Earnshaw’s Theorem, might there actually be shared-electron bonds? Is it possible to confirm their reality by seeing or feeling them? The spectacle of “clairvoyant” charlatans from the beginning of the 20th Century, who claimed to “see” details of atomic and molecular structure, contrasts with proper bases for scientific understanding. The molecular scale is not inconceivably small; indeed Newton and Franklin could perform simple experiments capable of measuring nanometer-scale distances. In the last 25 years various manifestations of Scanning Probe Microscopy have enabled chemists to “feel” individual molecules and atoms, but not bonds. For copyright notice see final page of this file

J.J. Thomson (1856-1940) Electron (1897) Plum-Pudding Atom © Cavendish Laboratpry, Cambridge University Electron (1897) Plum-Pudding Atom

Thomson's Model of Electron Configuration "consider the problem as to how 1…2…3…n corpuscles would arrange themselves if placed in a sphere filled with positive electricity of uniform density…" in “distributed in the way most amenable to mathematical calculation” “In default of exact knowledge of the nature of the way in which positive electricity occurs in the atom, we shall consider a case in which the positive electricity is distributed in the way most amenable to mathematical calculation, i.e., when it s=occurs as a sphere of uniform density, throughout which the corpuscles are distributed.” 1907 JJT "[We can] solve the special case where the corpuscles are confined to a plane." Thomson, Corpuscular Theory of Matter (1907)

Vortex Lattice Models (Greg Blonder www.genuineideas.com)                       http://www.genuineideas.com JJT went up to 100 particles (7 shells) p. 110 of “The Corpuscular Theory of Matter” 1907. Among these first 20 he had instead 9 =1 8 ; 13 = 3 10 ; 16 = 5 11 ; 19 = 1 7 11 ; and 20 = 1 7 12.

Thomson's Model of Electron Configuration "[We can] solve the special case where the corpuscles are confined to a plane." Thomson's Model of Electron Configuration "consider the problem as to how 1…2…3…n corpuscles would arrange themselves if placed in a sphere filled with positive electricity of uniform density…" in "the equilibrium of eight corpuscles at the corners of a cube is unstable."

Was Lewis ignorant of Earnshaw's Theorem? “I have ever since regarded [the cubic octet] as representing essentially the arrangement of electrons in the atom” G. N. Lewis (1923) Was Lewis ignorant of Earnshaw's Theorem? “Electric forces between particles which are very close together do not obey the simple law of inverse squares which holds at greater distances.” G. N. Lewis (1916) GNL, “Valence and the Structure of Atoms and Molecules”, 1923, p. 29 GNL, “The Atom and the Molecule”, JACS, 38, 763-785 (1916), p. 768

The Electron in Chemistry J. J. Thomson (1923) “… if [electron-nuclear attraction] were to vary strictly as the inverse square of the distance we know by Earnshaw's theorem than no stable configuration in which the electrons are at rest or oscillating about positions of equilibrium is possible ... … then a number of electrons can be in equilibrium about a positive charge without necessarily describing orbits around it.” I shall assume that the law of force between a positive charge and an electron is expressed by the equation F = Ee r2 1 atomic length scale (for distances r smaller than c, the force changes sign.) Couloumb r c r c

Quantum Mechanics (1926) Coulomb’s Law is just fine. Kinetic energy is reformulated to explain electron clouds and produce an "inverted" plum-pudding atom. Cubic octets and the ad hoc electrostatic force law soon disappeared from conventional Chemistry and Physics But shared-pairs and lone-pairs remained useful tools for discussing structure and bonding.

Earnshaw: No structure of minimum energy for point charges Classical

Despite Earnshaw, might there still be shared-pair bonds and lone pairs?

How do you know? By Seeing? Feeling?

Problem: ? Inconceivably Small

OCCULT CHEMISTRY A SERIES OF Clairvoyant Observations on the Chemical Elements BY ANNIE BESANT, P.T.S. AND CHARLES W. LEADBEATER Reprinted from the Theosophist. THEOSOPHIST OFFICE, ADYAR, MADRAS, S. THEOSOPHICAL PUBLISHING SOCIETY, LONDON AND BENARES CITY. 1909 (105 pp.) 1919 (123 pp.) 1951 (400 pp.)

The Occult Chemists (1895-1932) "Bishop" Charles Webster LEADBEATER (1847 - 1932) Mrs. Annie BESANT P.T.S. (1847-1933) Curuppumullage JINARAJADASA P.T.S. (~1877-1953) http://commons.wikimedia.org/wiki/Image:Charles_Webster_Leadbeater.001.jpg http://commons.wikimedia.org/wiki/Image:Annie_Besant_in_1897.JPG

H O N (1895) “Anu” Oxygen Hydrogen Atom Model in Charles Jencks’s Garden of Cosmic Speculation (1994) H O N (1895) 18 290 261 “Anu” constructed “with several scientists” Oxygen Hydrogen

Occult Atoms Iron 1008 Lithium 127 Neon 360 Helium 72

Bases for Scientific Belief: Occult Atoms 4f orbital e-density Neon 360 Bases for Scientific Belief: Evidence "cross-examine an assertion" 2) Logic Doubting Thomas was a scientist. John 20:24-29 3) Taste matures with experience Why should you believe the professor/text?

Occult Atoms Sodium 418

C Na Na2CO3 (1924) O "note that this trian-gular arrangement of O3 has just been deduced by Bragg from his X-ray analysis of Calcite"

Benzene (1924) "each of the three valencies of each Carbon are satisfied by Hydrogen, and the fourth valency, which some have postulated as going to the interior of the molecule, does actually do so." Cf. Question 6

Benzene “Resonance” H C (1889) H C H C

Honor Roll of (mostly) dead chemists G. N. Lewis Giuseppe Bruni (Bologna) Clean Slates Dedication: April, 1923

Sir William Crookes FRS, FTS (1832-1919) Supplied Li, Cr, Se, Ti, V, B, Be to Leadbeater and Besant (1907) 1861 - discovered Thallium developed Cathode Ray Tube invented Crookes Radiometer 1913-1916 - President of the Royal Society 1898 - President British Assn. for the Advancement of Science and The Society for Psychical Research "[Telepathic research] does not yet enlist the interest of the majority of my scientific brethren." Cartoon from “Vanity Fair” by "Spy" Sir Leslie Ward (1851 - 1922) http://commons.wikimedia.org/wiki/Image:Sir_William_Crookes_1902.jpg

Are Molecules Unobservably Small for “Vulgar Eyes”? 1 cm3 of water, 1/18 mole 6/18  1023 molecules molecules / cm ~ 3Å / H2O molecule

105 Lecture Room ~10 m Hair ~100 mm 101 10-4 10-9 Molecule ~1 nm 10-14 (again) Lecture Room ~10 m Hair ~100 mm 101 10-4 105 10-9 105 Molecule ~1 nm (small atom ~ 0.1 nm = 1 Å) Cf.Lecture 2:` magnetism, electrostatics, strong force on atomic scale 10-14 105 Nucleus ~10 fm

3/8  10-6  2.54 cm/inch ≈ 10-6 cm = 10 nm = 30 "waters" ! Newton Opticks (1717) p. 369 3/8  10-6  2.54 cm/inch ≈ 10-6 cm = 10 nm = 30 "waters" ! The length of a side of a cube containing 1 molecule of liquid water is about 1/3 nm 10^-6 cm is10 nm = 30 waters

Newton’s Rings convex to flat flat to 62 mm ~1 mm gap at rim 1 mm http://bednorzmuller87.phys.cmu.edu/demonstrations/optics/interference/demo326.html ~1 mm gap at rim

Newton Opticks (1717) air gap  51' Newton Opticks (1717) p. 175 pp.  = cos-1(0.29"/(12"51')) = 89.973° 0.29" air gap = (1251)(1-sin ) = 7  10-5 inch = 1.8 mm

Simpler Measurement of Smaller Distance 1774

Philosophical Transactions of the Royal Society 1774 Benjamin Franklin 1706-1790 http://moro.imss.fi.it/lavoisier Portrait of Benjamin Franklin (private collection) In receiving this painting on October 23 1783, Benjamin Franklin wrote to Madame Lavoisier the following: “I have long time been disabled from writing to my dear friend, by a severe fit of the gout, or I should have return’d my thanks for her kind present of the portrait, which she has herself done me the honour to make of me. It is allow’d by those who have seen it to have great merit as a picture in every respect; but what particularly endears it to me, is the hand who drew it.” Of this portrait Madame Lavoisier made two copies. One, the present, which was sent to Benjamin Franklin, the other which was retained by Madame Lavoisier and passed over Lavoisier's heirs. The latter was probably sold during the 1950s by Nelly de Chazelles and no photographic reproduction is known. http://www.historycarper.com/resources/twobf3/letter12.htm (halfway down the page) http://jcbmac.chem.brown.edu/scissorsHtml/chem/Avogadro/BenFranklin.html Portrait by Paulze Lavoisier 1783 http://moro.imss.fi.it/lavoisier

Benj. Franklin to Wm. Brownrigg (1773) …I had, when a youth, read and smiled at Pliny's account of a practice among the seamen of his time, to still the waves in a storm by pouring oil into the sea; as well as the use made of oil by the divers... I think that it has been of late too much the mode to slight the learning of the ancients. The learned, too, are apt to slight too much the knowledge of the vulgar.

Benj. Franklin to Wm. Brownrigg (1773) In 1757, being at sea in a fleet of ninety-six sail bound against Louisbourg, I observed the wakes of two of the ships to be remarkably smooth, while all the others were ruffled by the wind, which blew fresh. Being puzzled with the differing appearance, I at last pointed it out to our captain and asked him the meaning of it. "The cooks," said he, "have I suppose been just emptying their greasy water through the scuppers, which has greased the sides of those ships a little." … recollecting what I had formerly read in Pliny, I resolved to make some experiment of the effect of oil on water when I should have the opportunity.

Franklin's Experiment London, 1762 Clapham Common Franklin's Experiment London, 1762

Benj. Franklin to Wm. Brownrigg (1773) At length being at Clapham, where there is on the common a large pond which I observed one day to be very rough with the wind, I fetched out a cruet of oil and dropped a little of it on the water. I saw it spread itself with surprising swiftness upon the surface; but the effect of smoothing the waves was not produced; for I had applied it first on the leeward side of the pond where the waves were greatest; and the wind drove my oil back upon the shore. 1 tsp ≈ 5 cm3 I then went to the windward side where they began to form; and there the oil, though not more than a teaspoonful, produced an instant calm over a space several yards square which spread amazingly and extended itself gradually till it reached the lee side, making all that quarter of the pond, perhaps half an acre, as smooth as a looking glass. layer thickness ≈ 5 cm3 / 2 x 107 cm2 = 2.5 x 10-7 cm = 2.5 nm = 25 Å 0.5 acre ≈ 2000 m2 = 2 x 107 cm2

Benj. Franklin to Wm. Brownrigg (1773) When put on water it spreads instantly many feet round, becoming so thin as to produce the prismatic colours for a considerable space, and beyond them so much thinner as to be invisible except in its effect of smoothing the waves at a much greater distance. It seems as if a mutual repulsion between its particles took place as soon as it touched the water

Are there Electron Pairs Are there Electron Pairs? Scanning Probe Microscopy for Feeling Individual Molecules, Atoms, Bonds?

Scanning Tunneling Microscopy (1981) http://nobelprize.org Gerd Binnig http://nobelprize.org Heinrich Rohrer © IBY by permission Nobel Prize (1986)

Atomic Force Microscopy Gold coated Si Chip Only one of these five cantilevers is used in any one experiment. They differ in stiffness and ability to twist. 1.4 mm Hair The smallest scale division is 20 mm

Scanning Electron Micrographs of AFM Cantilever Tip 1m http://invsee.asu.edu/Invsee/listmod.htm Radius of curvature ~20 nm ©The IN-VSEE Project; Arizona State University 1999 http://invsee.asu.edu/Invsee/listmod.htm

Cantilever/Chip Holder Tips Cantilever/Chip Holder

Cantilever/Chip Holder Sensitive to < 1 molecule change in height !

fast Ledge Dissolution Rate slow slower Ledge Dissolution Rate AFM traces at 1 min intervals of part of the surface of a benzoin crystal dissolving in 95% water / 5% n-propanol. The larger pit is 5.1 nm deep. Each ledge is one “unit cell” (1.7 nm) high. 5 m (~600 molecules)

Scanning Tunneling Microscopy (1999) Graphite Br(CH2)11COOH on graphite O Br Geo. Flynn D. Yablon (Columbia Univ)

Permission limited by IBM Quantum corral STM Image of Fe atoms on Cu (1993) Permission limited by IBM Click to link to copyright webpage http://www.almaden.ibm.com:80/vis/stm/corral.html Reprint Courtesy of International Business Machines Corporation, copyright 1993 © International Business Machines Corporation

SNOM Scanning Near-Field Optical Microscope Scanning Near-Field Sample (scanned) Light Glass Fiber Aluminum Coating 100 nm Aperture Lens Emitted Light Detector

SNOM image of nanofabricated material mm scale red wavelength W. Brocklesby www.orc.soton.ac.uk by permission

Scanning Probe Microscopies (AFM, STM, SNOM) are really powerful. Sharp points can resolve individual molecules and even atoms but not bonds

Some Resonance Structures for H, C, N, O Isomers For quantum-calculated local-minimum-energy (valley) atomic arrangements

H, C, N, O isomers C in middle bad charge separation H C N O : + _ H C N O : H C N O : H C N O : + _ H C N O : + _ bad charge separation (most “electronegative” atom bears + charge) charge separation

H, C, N, O isomers N in middle better charge H C N O : + _ bad charge + _ H C N O : sestet H C N O : + _ H C N O : sestet : H C N O + _ : + _ H C N O sestet bad charge bad charge

H, C, N, O isomers O in middle : _ + H C N O : + _ sestet sestet H C N O : _ + H C N O : + _ sestet sestet bad charge bad charge

H, C, N, O isomers cyclic H C N O : + _ bad charge bad charge H C N O sestet sestet Lowest energy form can’t even be calculated. (downhill to open the ring)

HNCO isomers H C N O : _ + H C N O : + _ H C N O : + _ H C N O : H C N

150 100 50 200 HNCO isomers H C N O kcal/mole Ecalc

References: Most of these structures and energies were calculated at a very high level of theory as reported in Journal of Chemical Physics, 120, 11586-11599 (2004). The much less stable structures with O in the middle were calculated using the highest level of theory available in the Spartan 04 package of quantum programs. This program could not find an energy minimum for the cyclic structure with H on oxygen.

End of Lecture 4 Sept 9, 2009 Copyright © J. M. McBride 2009. Some rights reserved. Except for cited third-party materials, and those used by visiting speakers, all content is licensed under a Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0). Use of this content constitutes your acceptance of the noted license and the terms and conditions of use. Materials from Wikimedia Commons are denoted by the symbol . Third party materials may be subject to additional intellectual property notices, information, or restrictions.   The following attribution may be used when reusing material that is not identified as third-party content: J. M. McBride, Chem 125. License: Creative Commons BY-NC-SA 3.0