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Electron Filling (orbitals) in Periodic Table

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1 Electron Filling (orbitals) in Periodic Table
Objectives: To predict the highest energy sublevel for an element given its position in the periodic table. To predict the electron configuration for an element given its position in the periodic table. To predict the number of valence electrons for any representative element. To draw the electron dot formula for any representative element.

2 The Periodic Table * * Lanthanides Y Y Actinides Alkaline H He Li Be B
Noble gases Alkaline earth metals Halogens 1 18 H 1 He 2 2 13 14 15 16 17 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 Na 11 Mg 12 3 4 5 6 7 8 9 10 11 12 Al 13 Si 14 P 15 S 16 Cl 17 Ar 18 Transition metals K 19 Ca 20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 Alkali metals Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 Cs 55 Ba 56 * Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb 82 Bi 83 Po 84 At 85 Rn 86 Elements with the same valence electron configuration (elements located in the same column of the periodic table) have similar chemistry. Correlation is evident for the elements of Groups 1, 2, 3, 13, 16, 17, and 18. Intervening families in the p block (Groups 14 and 15) straddle the diagonal line separating metals from nonmetals. Noble gases (Group 18) have full valence electron shells. Alkali metals (Group 1) contain only a single electron outside a full shell. Fr 87 Ra 88 Y Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 Uun 110 Uuu 111 Uub 112 Uuq 113 Uuh 116 Uuo 118 * Lanthanides La 57 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho 67 Er 68 Tm 69 Yb 70 Lu 71 Y Actinides Ac 89 Th 90 Pa 91 U 92 Np 93 Pu 94 Am 95 Cm 96 Bk 97 Cf 98 Es 99 Fm 100 Md 101 No 102 Lr 103

3 Orbitals Being Filled Groups 1 8 2 1s 1 3 4 5 6 7 1s 2s 2 2p 3 3s 3p
1s 2s 2 2p 3 3s 3p 3d 4p Periods 4 4s 4d 5p 5 5s Blocks in the periodic table – The periodic table can be divided into “blocks” corresponding to the type of subshell that is being filled. – Two columns on the left are known as the s-block elements and consist of elements in which the ns orbitals are being filled. – Six columns on the right consist of elements in which the np orbitals are being filled and constitute the p block. – In between are the 10 columns of the d block elements in which the (n -1))d orbitals are filled. – At the bottom are the 14 columns of the f block, elements in which the (n - 2)f orbitals are filled. La 5d 6p 6 6s Ac 6d 7 7s 4f Lanthanide series 5f Actinide series Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 345

4 Electron Filling in Periodic Table
s s p 1 2 d 3 4 5 6 * 7 W f * W

5 Electron Filling in Periodic Table
metallic character increases nonmetallic character increases metallic character increases nonmetallic character increases

6 Periodic Table s s H He H p Li Be B C N O F Ne Na Mg d Al Si P S Cl Ar
1 He 2 H 1 p 1 1 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 2 2 Na 11 Mg 12 d Al 13 Si 14 P 15 S 16 Cl 17 Ar 18 3 3 K 19 Ca 20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 4 4 Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 5 5 Cs 55 Ba 56 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb 82 Bi 83 Po 84 At 85 Rn 86 6 6 * * Fr 87 Ra 88 Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 7 7 W W f La 57 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho 67 Er 68 Tm 69 Yb 70 Lu 71 * Ac 89 Th 90 Pa 91 U 92 Np 93 Pu 94 Am 95 Cm 96 Bk 97 Cf 98 Es 99 Fm 100 Md 101 No 102 Lr 103 W

7 Melting Points He H He Mg Symbol Melting point oC Li Be B C N O F Ne
0.126 H -259.2 He -269.7 1 1 Mg 650 Symbol Melting point oC Li 180.5 Be 1283 B 2027 C 4100 N -210.1 O -218.8 F -219.6 Ne -248.6 2 2 > 3000 oC oC Na 98 Mg 650 Al 660 Si 1423 P 44.2 S 119 Cl -101 Ar -189.6 3 3 K 63.2 Ca 850 Sc 1423 Ti 1677 V 1917 Cr 1900 Mn 1244 Fe 1539 Co 1495 Ni 1455 Cu 1083 Zn 420 Ga 29.78 Ge 960 As 817 Se 217.4 Br -7.2 Kr -157.2 4 4 Rb 38.8 Sr 770 Y 1500 Zr 1852 Nb 2487 Mo 2610 Tc 2127 Ru 2427 Rh 1966 Pd 1550 Ag 961 Cd 321 In 156.2 Sn 231.9 Sb 630.5 Te 450 I 113.6 Xe -111.9 5 5 Cs 28.6 Ba 710 La 920 Hf 2222 Ta 2997 W 3380 Re 3180 Os 2727 Ir 2454 Pt 1769 Au 1063 Hg -38.9 Tl 303.6 Pb 327.4 Bi 271.3 Po 254 At Rn -71 6 6 Ralph A. Burns, Fundamentals of Chemistry , 1999, page 1999

8 Elements with Highest Densities
Year Density Element Discovered (g/cm3) Osmium Iridium Platinum Rhenium Neptunium Plutonium Gold prehistoric Tungsten Uranium Tantalum

9 Densities of Elements H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K
0.071 He 0.126 1 1 Li 0.53 Be 1.8 B 2.5 C 2.26 N 0.81 O 1.14 F 1.11 Ne 1.204 2 2 Na 0.97 Mg 1.74 Al 2.70 Si 2.4 P 1.82w S 2.07 Cl 1.557 Ar 1.402 3 3 K 0.86 Ca 1.55 Sc (2.5) Ti 4.5 V 5.96 Cr 7.1 Mn 7.4 Fe 7.86 Co 8.9 Ni 8.90 Cu 8.92 Zn 7.14 Ga 5.91 Ge 5.36 As 5,7 Se 4.7 Br 3.119 Kr 2.6 4 4 Rb 1.53 Sr 2.6 Y 5.51 Zr 6.4 Nb 8.4 Mo 10.2 Tc 11.5 Ru 12.5 Rh 12.5 Pd 12.0 Ag 10.5 Cd 8.6 In 7.3 Sn 7.3 Sb 6.7 Te 6.1 I 4.93 Xe 3.06 5 5 Cs 1.90 Ba 3.5 La 6.7 Hf 13.1 Ta 16.6 W 19.3 Re 21.4 Os 22.48 Ir 22.4 Pt 21.45 Au 19.3 Hg 13.55 Tl 11.85 Pb 11.34 Bi 9.8 Po 9.4 At --- Rn 4.4 6 6 Element Year Discovered Density (g/cm3) Osmium Iridium Platinum Rhenium Neptunium Plutonium Gold prehistoric Tungsten Uranium Tantalum 8.0 – 11.9 g/cm3 12.0 – 17.9 g/cm3 > 18.0 g/cm3 Mg 1.74 Symbol Density in g/cm3C, for gases, in g/L W

10

11 4f 4d 4p 4s n = 4 Sublevels 3d 3p 3s n = 3 Energy 2p 2s n = 2 1s n = 1

12 H He H Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe
1 He 2 H 1 1 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 2 Na 11 Mg 12 Al 13 Si 14 P 15 S 16 Cl 17 Ar 18 3 K 19 Ca 20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 4 Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 5 Cs 55 Ba 56 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb 82 Bi 83 Po 84 At 85 Rn 86 6 * Fr 87 Ra 88 Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 7 W La 57 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho 67 Er 68 Tm 69 Yb 70 Lu 71 Ac 89 Th 90 Pa 91 U 92 Np 93 Pu 94 Am 95 Cm 96 Bk 97 Cf 98 Es 99 Fm 100 Md 101 No 102 Lr 103

13 Electron Filling in Periodic Table
s s s s H 1s1 He 1s2 H 1s1 p p 1 1 Li 2s1 Be 2s2 B 2p1 C 2p2 N 2p3 O 2p4 F 2p5 Ne 2p6 2 2 Na 3s1 Mg 3s2 d d Al 3p1 Si 3p2 P 3p3 S 3p4 Cl 3p5 Ar 3p6 3 3 K 4s1 Ca 4s2 Sc 3d1 Ti 3d2 V 3d3 Cr 3d5 Mn 3d5 Fe 3d6 Co 3d7 Ni 3d8 Cu 3d10 Zn 3d10 Ga 4p1 Ge 4p2 As 4p3 Se 4p4 Br 4p5 Kr 4p6 4 4 Rb 5s1 Sr 5s2 Y 4d1 Zr 4d2 Nb 4d4 Mo 4d5 Tc 4d6 Ru 4d7 Rh 4d8 Pd 4d10 Ag 4d10 Cd 4p1 In 5p1 Sn 5p2 Sb 5p3 Te 5p4 I 5p5 Xe 5p6 5 5 Cs 6s1 Ba 6s2 Hf 5d2 Ta 5d3 W 5d4 Re 5d5 Os 5d6 Ir 5d7 Pt 5d9 Au 5d10 Hg 5d10 Tl 6p1 Pb 6p2 Bi 6p3 Po 6p4 At 6p5 Rn 6p6 6 6 * * by Anthony Carpi, Ph.D. Electron Configuration and the Table The "periodic" nature of chemical properties that Mendeleev had discovered is related to the electron configuration of the atoms of the elements. In other words, the way in which an atom's electrons are arranged around its nucleus affects the properties of the atom. Bohr’s theory of the atom tells us that electrons are not located randomly around an atom's nucleus, but they occur in specific electron shells.  Each shell has a limited capacity for electrons.  As lower shells are filled, additional electrons reside in more-distant shells. The capacity of the first electron shell is two electrons and for the second shell the capacity is eight. Thus, in our example discussed above, oxygen, with eight protons and eight electrons, carries two electrons in its first shell and six in its second shell. Fluorine, with nine electrons, carries two in its first shell and seven in the second. Neon, with ten electrons, carries two in the first and eight in the second. Because the number of electrons in the second shell increases, we can begin to imagine why the chemical properties gradually change as we move from oxygen to fluorine to neon. Sodium has eleven electrons. Two fit in its first shell, but remember that the second shell can only carry eight electrons. Sodium's eleventh electron cannot fit into either its first or its second shell. This electron takes up residence in yet another orbit, a third electron shell in sodium. The reason that there is a dramatic shift in chemical properties when moving from neon to sodium is because there is a dramatic shift in electron configuration between the two elements. But why is sodium similar to lithium? Let's look at the electron configurations of these elements. Group IA VIA VIIA VIIIA Lithium Oxygen Fluorine Neon Sodium Electron Configurations for Selected Elements As you can see in the illustration, while sodium has three electron shells and lithium two, the characteristic they share in common is that they both have only one electron in their outermost electron shell. These outer-shell electrons (called valence electrons) are important in determining the chemical properties of the elements. An element's chemical properties are determined by the way in which its atoms interact with other atoms. If we picture the outer (valence) electron shell of an atom as a sphere encompassing everything inside, then it is only the valence shell that can interact with other atoms - much the same way as it is only the paint on the exterior of your house that "interacts" with, and gets wet by, rain water. An atom's valence shell "covers" inner electron shells The valence shell electrons in an atom determine the way it will interact with neighboring atoms, and therefore determine its chemical properties. Since both sodium and lithium have one valence electron, they share similar chemical properties. Electron Configuration Shorthand: For elements in groups labeled A in the periodic table (IA, IIA, etc.), the number of valence electrons corresponds to the group number. Thus Li, Na, and other elements in group IA have one valence electron. Be, Mg, and other group-IIA elements have two valence electrons. B, Al and other group-IIIA elements have three valence electrons, and so on. The row, or period, number that an element resides in on the table is equal to the number of total shells that contain electrons in the atom. H and He in the first period normally have electrons in only the first shell; Li, Be, B, and other period-two elements have two shells occupied, and so on. To write the electron configuration of elements, scientists often use a shorthand in which the element's symbol is followed by the element's electron shells, written as a right-hand parentheses symbol ")". The number of electrons in each shell is then written after the ) symbol. A few examples are shown below. Element   Configuration Shorthand Hydrogen        H )1e- Lithium        Li )2e- )1e- Fluorine        F  )2e- )7e-        Na )2e- )8e- )1e-  Fr 7s1 Ra 7s2 Rf 6d2 Db 6d3 Sg 6d4 Bh 6d5 Hs 6d6 Mt 6d7 7 7 W W f f La 5d1 Ce 4f2 Pr 4f3 Nd 4f4 Pm 4f5 Sm 4f6 Eu 4f7 Gd 4f7 Tb 4f9 Dy 4f10 Ho 4f11 Er 4f12 Tm 4f13 Yb 4f14 Lu 4f114 * * Ac 6d1 Th 6d2 Pa 5f2 U 5f3 Np 5f4 Pu 5f6 Am 5f7 Cm 5f7 Bk 5f8 Cf 5f10 Es 5f11 Fm 5f14 Md 5f13 No 5f14 Lr 5f14 W W

14 Names and Symbols of Selected Elements
Name* Symbol Name* Symbol Aluminum Al Lead (plumbum) Pb Argon Ar Lithium Li Barium Ba Magnesium Mg Boron B Mercury (hydrargyrum) Hg Bromine Br Neon Ne Cadmium Cd Nickel Ni Calcium Ca Nitrogen N Carbon C Oxygen O Chlorine Cl Phosphorus P Cobalt Co Potassium (kalium) K Copper (cuprum) Cu Silicon Si Fluorine F Silver (argentum) Ag Gold (aurum) Au Sodium (natrum) Na Helium He Strontium Sr Hydrogen H Sulfur S Iodine I Tin (stannum) Sn Iron (ferrum) Fe Zinc Zn *Names given in parentheses are ancient Latin or Greek words from which the symbols are derived.

15 A plumbob is heavy and used by carpenters to build walls straight
A plumbob is heavy and used by carpenters to build walls straight. The word lead in latin is plumbum meaning heavy. Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

16 Electronegativity The ability of an atom in a molecule
to attract shared electrons to itself. The Pauling electronegativity scale – Based on measurements of the strengths of covalent bonds between different elements – Pauling arbitrarily set the electronegativity of fluorine at 4.0, thereby creating a scale in which all elements have values between 0 and 4.0 – Electronegativities increase diagonally from the lower left to the upper right of the periodic table; elements lying on diagonal lines running from the upper left to lower right tend to have comparable values – Pauling’s method is limited by the fact that many elements do not form stable covalent compounds with other elements – Pauling scale is based on the properties of atoms in molecules LINUS PAULING A Biography Linus Pauling was born with twin legacies. Although his parents could give him very little in the way of material wealth, they did give him the better gift of great intelligence. His brilliant mind eventually provided him with financial security as well as his greatest happiness. It can also be argued that this gift of intelligence was responsible for the controversy that seemed to surround everything he did and everything he wrote. He made great intuitive leaps and was frequently criticized for the conclusions he drew from what some felt was too little experimentation, often outside of Pauling's area of expertise. His father was part pharmacist and part "medicine man" and wasn't especially successful at either. At the time when Linus was born in 1901 the family was living in what is now the wealthiest suburb of Portland, Oregon. However, they lived a very precarious existence at the edges of poverty. In fact, when Linus was four, the family moved to his mother's home town of Condon to get financial aid from her family. Condon is a small town in north central Oregon and in many ways then (and now) was a stereotypical 'Western' town with one main street and false fronts on many of the business buildings. In Condon his father took over the town drug store and Linus began exploring the physical world around him. A small creek flows on the south edge of town. There he and a friend explored the rocky creek bed and collected some of the minerals for which Pauling would eventually establish structures at the California Institute of Technology . It was likely during this time in Condon that Pauling developed his antipathy to snow and very cold weather. Condon's altitude is about 4000 feet and during the winter the temperature may not go above -20 Fahrenheit for days at a time. The wind roars through town because the town sits on top of the Columbia Basalt plateau and for miles around there is nothing to deflect the winds. The Pauling family moved back to Portland just after Linus began school. When he was nine, his father died, leaving Linus, his two younger sisters and their mother to make their own way in the world. This began a stretch of more than 15 years when Pauling tried to pursue his education, while his mother tried to get him to quit school and become the support of the family. He did not quit school. However, he did find many ingenious ways to make money and most of it went to help support his mother and sisters. By the time he was twelve he was a freshman at Washington High School in Portland. After four years of learning, with or without the help of his teachers, and of odd jobs (delivering milk, running film projectors, and even working in a shipyard, for example) he left high school. He did not graduate because the high school required their students to take a class in civics and Pauling saw no reason why he should since he could absorb any of that from his own reading. Later, after his Nobel Prize for Peace in 1962, the administration agreed that he had learned civics on his own by granting him his high school diploma. In the fall of 1917 Pauling enrolled in Oregon Agricultural College-now Oregon State University-in Corvallis, Oregon. He sailed through the freshman courses required of a chemical engineering major in spite of the fact that he was also working one hundred hours a month. He was not only supporting himself, but also providing the bulk of his family¹s support. This became more and more arduous after his mother became ill. In fact, he did not return to the college after his sophomore year because of the need for money. However, at the first of November of what would have been his junior year, he received an offer to become an instructor of quantitative analysis at Oregon Agricultural College, a course he had just taken as a sophomore! The offer included a salary of $100 a month and he gladly took it. He himself did not take any courses that year. He met his future wife, Ava Helen Miller, when she was a student in his quantitative analysis class. When he had graduated with his degree in chemical engineering, his mother again began pressuring him to stop his education and make money, perhaps become a secondary school teacher. Pauling, however, had applied to graduate schools at Harvard, Berkeley and the fairly new California Institute of Technology. His first choice was Berkeley because G.N. Lewis himself was the chair of the chemistry department, but Berkeley was too slow in replying to his application. Harvard didn't really interest him much, so his decision was made in favor of Cal. Tech. One year after begining work at Cal. Tech. he married Ava Helen Miller. At the California Institute of Technology his advisor was Roscoe Dickinson, whose area of expertise was X-ray crystallography. At this time Dickinson was investigating the crystal structure of various minerals. In his work with Dickinson, Pauling displayed what was to become his standard method of attacking a problem. According to Dr. Edward Hughes, "He would guess what the structure might be like, and then he would arrange it to fit into the other data. . . he could then calculate the intensities he would get from that structure and then compare it with the observed ones." For the rest of his career Pauling was criticized for using too large an amount of intuition in his work and not always having complete data to back up what he wrote. As well as doing his research work, Pauling was taking courses and serving as a teaching assistant in the freshman chemistry course. He received his Ph. D. in chemistry with high honors in the June of His dissertation comprized the various papers he had already published on the crystal structure of different minerals. A year later, when he was 25, he received a Guggenheim fellowship to study at the University of Munich under Arnold Sommerfeld, a theoretical physicist. Here he began work with quantum mechanics. In January of 1927 he published "The Theoretical Prediction of the Physical Properties of Many Electron Atoms and Ions; Mole Refraction, Diamagnetic Susceptibility, and Extension in Space" in which he applied the concept of quantum mechanics to chemical bonding. In March, a heated exchange took place between Pauling and W.L. Bragg in London over this paper. Bragg believed that Pauling had used some of his ideas without giving him credit for them. According to Pauling, the ideas originated in a paper by Gregor Wentzel on quantum mechanical calculations for electrons in complex atoms. "Wentzel reported poor agreement between the calculated and experimental values, but I found that his calculation was incomplete and that when it was carried out correctly, it led to values... in good agreement with the experimental values." In 1928 he published six principles to decide the structure of complicated crystals. This bothered Bragg even more since they did not all originate with Pauling. Actually, according to Horach Judson, "Pauling clarified them, codified them, demonstrated their generality and power." However, Bragg was spreading stories in England about Pauling's "thievery" and lack of professional ethics. At this time Pauling took an assistant professorship in chemistry at Cal. Tech. There was a discrepancy, however, in what he thought he was being offered and what he was actually given. He had thought he was taking an appointment as Assistant Professor of Theoretical Chemistry and Mathematical Physics. This misunderstanding seems to have been a thorn in his side. However, thorn or no thorn, he began a period of intense and productive work. In 1928 he published a paper on orbital hybridization and resonance. In 1931 he published the first paper, "The Nature of the Chemical Bond". At this time he was also teaching classes. One of his responsibilities was the freshman chemistry course. Richard Noyes, now professor emeritus of physical chemistry at the University of Oregon, remembers that Pauling was an exciting lecturer and had an unbelievable ability as a demonstrator. He would be explaining something and "suddenly his mind would go off in a new direction, frequently into areas where the freshmen couldn't follow him." Dr. Noyes remembers one redox titration when Pauling turned on the buret then stepped to the chalkboard and began to write the equation for the reaction. He was glancing at the flask in which the reaction was taking place and suddenly moved back to the buret and turned it off, then swirled the mixture in the flask. The color was perfect, a perfect endpoint! In 1931 Pauling was awarded the Langmuir Prize of the American Chemical Society for "the most noteworthy work in pure science done by a man under 30 years of age." In the same year he was offered a joint full professorship in both chemistry and physics at the Massachusetts Institute Of Technology. He seriously considered the offer but he didn't want to have to brave the Massachusetts' winters. He ended up by accepting the position for one year only. In 1933 he was made a member of the National Academy of Sciences. He was 32, the youngest appointment to this body ever made. Pauling was later to write, "By 1935, I had worked out most of the fundamental problems connected with the chemical bond." and "My serious interest in what is now called molecular biology began about 1935." He began with a look at hemoglobin. He discovered that the hemoglobin in arteries is repelled by a magnet while that in the veins is attracted to a magnet. His answer to this puzzle resulted in a paper on oxygen's binding to hemoglobin in The work on hemoglobin also lead to work on hydrogen-bonding between the polypeptide chains in proteins and another paper that same year on the denaturing of proteins. Also in 1936, he was made chairman of the Division of Chemistry and Chemical Engineering at Cal. Tech. In 1939 he published his most important book, The Nature of the Chemical Bond. His work on hydrogen-bonding in proteins lead him to develop a theory of protein structure. It was generally accepted that proteins were made up of polypeptide chains which were, in turn, made up of long strings of amino acids, bonded end to end. He tried to demonstrate a way of coiling the polypeptide chain in the protein alpha keratin to match the x-rays that crystallographer W.T. Astbury had taken and interpreted, but was unable to fit a model to the data. Working with Corey, he did establish the structures of many small peptides and established that the peptide bond holding amino acids together is planar. In 1939 they formulated a small set of structural conditions for any model of a popypeptide chain. Finally, in 1948, Pauling worked out the alpha helix structure of a polypeptide. He was in Oxford at this time, confined to bed with nephritis and bored with what he had to read. He says, "I took a sheet of paper and sketched the atoms with the bonds between them and then folded the paper to bend one bond at the right angle, what I thought it should be relative to the other, and kept doing this, making a helix, until I could form hydrogen bonds between one turn of the helix and the next turn of the helix, and it only took a few hours doing that to discover the alpha-helix." In 1954 Linus Pauling was given the Nobel Prize for Chemistry for his work on molecular structure, especially proteins. During World War II Pauling worked on various "war" projects as did everyone at Cal. Tech. He chose not to work on the Manhattan Project, however. At the same time his wife was becoming more and more involved in socialist politics. They fought the internment of their Japanese-American gardener and, with the American Civil Liberties Union, the internment of all the Japanese-Americans. He was also becoming more and more worried about the atomic bomb and the radiation it produced. He became involved in the Scientists Movement, a more-or-less nation-wide group of scientists working for safe control of nuclear power. The Movement believed in ³the necessity for all nations to make every effort to cooperate now in setting up an international administration with police powers which can effectively control at least the means of nuclear warfare.² His wife was a member of the Women's International League for Peace and Freedom. In fact, at this time, she was probably more outspoken on the issues of human rights, peace and the banning of nuclear testing than Pauling was. In 1947 President Truman awarded him the presidential Medal of Merit for his work on crystal structure, the nature of the chemical bond, and his efforts to bring about world peace. In November of 1950, he was subpoenaed to appear before the Senate Investigating Committee on Education of the State of California. He testified for over two hours, "mainly about my reasons for objecting to special loyalty oaths involving inquiry into political beliefs." He wrote the next day, "My own political beliefs are well known. I am not a Communist. I have never been a Communist. I have never been involved with the Communist Party. I am a Rooseveltian Democrat." However, he also believed that no governmental body had the right to ask him to answer those same questions under oath. This was during the early days of the McCarthy "witch hunts", which were stronger at the time in California than at most other places. His position upset some of the trustees and some professors at Cal .Tech., who tried to oust him. This was just after Pauling, working with Corey, had used the idea gained from his paper model to work out the structure of many different protein molecules, all of which contained his alpha-helix. His proposed structure was not immediately accepted by the scientific world, however, especially by scientists in England. Therefore, in January of 1952, Pauling requested a passport to attend a meeting in England, specifically to defend his ideas. The passport was denied because granting it "would not be in the best interest of the United States." He applied again and wrote President Eisenhower, asking him to arrange the issuance of the passport since, "I am a loyal citizen of the United States. I have never been guilty of any unpatriotic or criminal act." The answer came back asking him to provide the State Department with some evidence supporting his claims. He sent a statement, made under oath, stating that he was not a communist, never had been a communist, and had never been involved with the Communist Party. The state department replied that his "anti-communist statements were not sufficiently strong" and again denied the passport on the very day he was supposed to leave for the conference. This pattern of Pauling requesting a passport to attend various conferences and the state department denying the application continued for a little over two years. During this time Einstein wrote a letter to the state department supporting Pauling's right to have a passport. He also wrote Pauling telling him, "It is very meritorious of you to fight for the right to travel." In 1953 Pauling published his book, No More War. Again in April of 1954, when he requested a passport, he was denied it. On November 3 of that year, while he was giving a "routine lecture" on hemoglobin at Cornell University, he was called to the telephone to learn that he had just been awarded the Nobel Prize in Chemistry. His first worry was, would he be able to get a passport so he could accept the prize in person? He applied immediately and for weeks he heard nothing. In Washington there were strong voices opposing the granting of the passport. One senator asked, "Are you in the State Department allowing some group of people in some foreign country to determine which Americans get passports?" On November 27, however, barely two weeks before the ceremony in Sweden, his passport did arrive. His years of being unable to get a passport did more than inconvenience him. In 1948 he was already working toward a description of the structure of DNA. By the early 1950's, Rosalind Franklin and others working at Kings College in London had taken some of the sharpest, most detailed photographs of DNA ever. These are what Watson and Crick used in their successful discovery of the DNA double helix. Had Pauling been able to attend the spring 1952 conference he would likely have seen these photographs and might have come to the same conclusion, before Watson and Crick. It is sure that his not seeing them contributed to his proposed structure which had the phosphate groups closely packed inside a single helix with the bases sticking out around the outside. Pauling continued his political activism, particularly his protesting of atomic bomb testing. This culminated in a petition to the United Nations--signed by 11,021 scientists from around the world--calling for an immediate world-wide ban on nuclear testing. Because of this petition he was subpoenaed to appear before the U.S. Senate Internal Security Committee. The committee wanted him to give the names of the petitioning scientists. Under oath, he admitted that he, Barry Commoner, and Edward Condon had initiated the petition, but refused to give any more names. There was much applause from the gallery and, after a while, the committee backed down. Later, during the Kennedy Administration, after Kennedy had decided to go ahead with atmospheric nuclear testing, Pauling sent President Kennedy a telegram asking, ³Are you to give the orders that will cause you to go down in history as one of the most immoral men of all times and one of the greatest enemies of the human race?² Of course, this telegram raised quite a furor. However, the Kennedys still invited him to a White House dinner honoring Nobel Prize winners of the western hemisphere. On the day of the dinner, both Dr. and Mrs. Pauling took part in a demonstration in front of the White House, then left the picket line to go in to dinner. Later that evening, Pauling even danced with Mrs. Kennedy. On October 10, 1962, it was announced that Linus Pauling had been awarded the Nobel Peace Prize for his efforts on behalf of a nuclear test ban treaty. This award was not universally popular. Many newspapers and magazines printed editorials denouncing him, his activism,and his having been given the prize. Since his second Nobel Prize, Dr. Pauling has researched the chemistry of the brain and its effect on mental illness, the cause of sickle-cell anemia and what is happening to the hemoglobin in the red blood cells of people with this disease, and the effects of large doses of vitamin C on both the common cold and some kinds of cancer. He recently published papers on high temperature super conductivity. He has worked at the University of California at San Diego, at Stanford and at the Linus Pauling Institute for Medical Research. He has won many awards in chemistry, including all the major ones. He remains, as he has been all his life, a brilliant man with brilliant ideas. He was once asked by a high school student , "How can I have great ideas?" Pauling's answer was, "The important thing is to have many ideas." He has certainly followed his own advice. References 1. A. Serafini, Linus Pauling A Man and His Science, Paragon House, New York, N.Y., A.J. Ihde, The Development of Modern Chemistry, Dover, New York, N.Y., 1984, pp. 543 & 544, p 551. 3. J. H. Sturdivant, "The Scientific Work of Linus Pauling", A. Rich & N. Davidson, Structural Chemistry and Molecular Biology, W.H. Freeman and Co., San Francisco, CA, 1968, pp. 16, 18, 19. 4. D.C. Hodgkin & D.P. Riley, "Some Ancient History of Protein X-Ray Analysis", A.Rich and N. Davidson, Structural Chemistry and Molecular Biology, W.H. Freeman and Co., San Francisco, Ca.,1968, pp. 7, 8, 16, 18, 19. 5. "Pauling, Linus Carl", S.P. Parker, ed., McGraw-Hill Encyclopedia of Chemistry, Volume 9, McGraw-Hill, New York, N.Y., 1982, pp Linus Pauling

17 Electronegativities Period H B P As Se Ru Rh Pd Te Os Ir Pt Au Po At
2.1 B 2.0 P As Se 2.4 Ru 2.2 Rh Pd Te Os Ir Pt Au Po At 1 1 2A 3A 4A 5A 6A 7A Actinides: Li 1.0 Ca Sc 1.3 Sr Y 1.2 Zr 1.4 Hf Mg La 1.1 Ac Lanthanides: * y Be 1.5 Al Si 1.8 Ti V 1.6 Cr Mn Fe Co Ni Cu 1.9 Zn 1.7 Ga Ge Nb Mo Tc Ag Cd In Sn Sb Ta W Re Hg Tl Pb Bi N 3.0 O 3.5 F 4.0 Cl C 2.5 S Br 2.8 I 2 2 Na 0.9 K 0.8 Rb Cs 0.7 Ba Fr Ra Below 1.0 3 3 3B 4B 5B 6B 7B 8B 1B 2B Period 4 4 5 5 6 6 Linus Pauling ( ) awarded Nobel Prize in chemistry in 1954 for his 1939 text, The Nature of the Chemical Bond, and also won the Nobel Peace Prize in 1962 for his fight to control nuclear weapons. The greater the electronegativity of an atom in a molecule, the more strongly it attracts the electrons in a covalent bond. • Elements with high electronegativities tend to acquire electrons in chemical reactions and are found in the upper-right corner of the periodic table. • Elements with low electronegativities tend to lose electrons in chemical reactions and are found in the lower-left corner of the periodic table. 7 Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 373

18 Covalent Bonds Polar-Covalent bonds Nonpolar-Covalent bonds
Electrons are unequally shared Electronegativity difference between 0.3 and 1.7 Example: H2O (water) O = 3.5 difference is 1.4 H = 2.1 Metals – Elements with a low electronegativity and that have electron affinities that have either positive or small negative values and small ionization potentials – Are good electrical conductors that tend to lose their valence electrons in chemical reactions (they are reductants) Semimetals – Elements with intermediate electronegativities – Elements that have some of the chemical properties of both nonmetals and metals Nonpolar-Covalent bonds Electrons are equally shared Electronegativity difference of 0 to 0.3


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