JACS AT 125
ATOMIC DISTANCES Linus Pauling's landmark paper in 1947 predicts metallic radii of most elements
istry "for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances." Pauling's wife, Ava Helen, was a peace activist who urged him to take up the cause. His outspoken antiwar stance landed him in trouble with the government and Caltech trustees. But Pauling won another Nobel Prize, this time for peace, in 1962. In 1963, he left Caltech to
INUS C. PAULING SPENT A GOOD came to know Pauling and his family well. chunk of his career developing He explains how Pauling used his "martheories about chemical bonds. velous chemical intuition" to describe the During the 1930s, he wrote a se- complexities of metallic bonding and to ries ofpapers on the subject, cul- predict their radii. minating in his famous book "The Nature An atomic radius can be of the Chemical Bond." For the most part, envisioned as a hook stickhis work back then focused on bonds that ing out from the center of are covalent, such as those found in car- the atom. When it grabs a bon tetrachloride. hook on another atom, the But in 1947, he again broke ground, this combination of the two time in his exploration of metallic bonds. radii equals the bond The article 'Atomic Radii and Interatom- length, Hedberg says. ic Distances in Metals," published in the Pauling theorized that Journal of theAmerican Chemical Society [69,bonds in metals are similar 542 (1947)}, predicted the metallic radii of to some covalent bonds, in most elements—illustrated in a periodic that they "resonate." In typtable. The article is the 79th most cited in ical metallic lattices, atoms the journal's 125-year history, underscor- can take on a body-cening the paper's lasting influence. tered cubic structure with To be sure, Pauling's eminence imbued a nine-atom unit or a facecentered cubic structure most of his work. "One of the reasons this paper is cited a lot is that everything Paul- with a 13-atom unit. ing did was cited a lot," says Kenneth W. An atom such as, say, strontium, has two valence MULTITALENTED Pauling, photographed in about Be B LI electrons available for 1960, teaches with molecular models. In the V 1 3 2 bonding. But, explains Hed- foreground is a model of the a-helix structure he R(CN12) 1.549 1.123 0.98 berg, an atom in the center proposed for proteins, another of his great 0.889 1.225 0.8 RID of a body-centered cubic achievements. structure is surrounded by Mg Na Al eight more atoms. The only way it can bind join the faculty of Stanford University V 1 2 3 Later in his life, Pauling became a pro1.896 1.598 1.429 to all of them is to resonate, Pauling reaRICN12) 1.364 1.248 1.572 RIU soned. An atom with more valence elec- ponent of the healing powers of vitamin trons can form stronger bonds, which are C and founded the Pauling Institute for Sc K Ca shorter, making the atomic radius smaller. Medical Research in Palo Alto, Calif. In 2 V 1 3 1986, Pauling bequeathed his andhis wife's With equations derived from his work 2.349 1.97 1.62 RICN12) personal and professional memorabilia to on covalent bonds, Pauling predicted the 2.025 1.736 1.439 RID bond lengths for the metallic radius of an OSU (C&EN, Aug. 7, 2000, page 62). PERIODIC A segment of Pauling's atom in the center of a face-centered cu- Pauling donated about 10,000 to 15,000 table of metallic atomic radii shows bic unit (coordination number 12). He al- items to OSU each year until his death in the atoms' valence (v), the metallic so predicted the metallic radii for the case 1994. Pauling's friends and colleagues also reradii of the atoms with a of a single atom bound to another. coordination number of 12 in a Pauling was born in 1901, in Portland, member him as a gifted communicator, as face-centered cubic lattice Oregon. He attended Oregon Agricultur- hisJACS paper on metallic radii of the el[RfCNf 2|], and the metallic radii of al College in Corvallis, which would later ements demonstrates. "I took great pleasure in rereading this the atoms singly bonded to one become OSU, and obtained his bachelor's other atom [R(1)]. degree in chemical engineering in 1922. article," Hedberg says. "He wrote just as He then went to Caltech for graduate he spoke—it flowed right out of him."— Hedberg, emeritus chemistry professor at school, and in 1928 joined the faculty there ELIZABETH WILSON Oregon State University (OSU), Corvallis. as an assistant professor of theoretical Hedbergwas first agraduate student and chemistry Pauling's career was extraordi- C&EN is celebrating the 125th volume of the then a researcher at California Institute of narily diverse, and included work on X-ray Journal of the American Chemical Society Technology while Pauling was chairman of crystallography and the structure of DNA. by featuring selectedpapersfrom among its 125 the chemistry department there. Hedberg In 1954, he won the Nobel Prizeiri Chem.- most cited. Thispaper was ranked 79 th.
L
30
C&EN / MARCH 24, 2003
HTTP //WWW CEN-ONLINE ORG
