An electronegativity spectrum for the periodic table - Journal of

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An Electronegativity Spectrum

W. B. Guenther University of the South Sewanee, Tennessee 37375

for the Periodic Table

Anyone who looks through the history of periodic tables of the elements in Rlazurs' hook' and in almost every volume of THIS JOURNAL, may well conclude that no imaginable ideas in two- or threedimensional arrangements have gone untried. For general instructional uses, the long form prevalent now represents some improvement over the folded Mendeleev table formerly seen in classrooms. However, the faults of these forms continue to stimulate attempts at revision. Some faults of common tables are 1) The meaningless empty space s t the top between groups I1 and 111. 2) Putting H aver Li or F. 3) The illogic (for geometric reasons) of putting the d-transition elements in order between s and v ,. while releeatine-.f-transition elements to a footnote. 4) Attempts to convey properties with notations in each sqnae. This makes a confusing clutter on some charts.

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The table pictured in this note eliminates these faults by using a spectrum of colors coded to electronegativities, and giving s, p, d, and f blocks equal legitimacy in the family of elements. An attractive and instructive chart resulted, but novelty for the ideas cannot be claimed. Arrangement by electronic structure has many precedents,' and was employed recently I n a table made in a widely used table by E i ~ h i n g e r . ~ to show size and electronegativity relations, Sanderson used colored plastic spheres3 A few special features of the present color table are 1) H snd He, which might. be called the cosmic elements, are unique in their small atomic sise, properties, and cosmic %bundance. They receive a separate location. 2 ) The large differences between top row elements and their familiw below them, come out in color changes, except for C-B. 3) Some often-mentioned diagonal relations show well: LiMg, Be-AI, etc. 4 ) The chemical similarity among the f-filling elements shows in their single color. 5) Size effecte resulting from the filling of d and f orbitals, show up in t,he orange section of t,he d-elements. These are among the acid sulfide precipitating elements in qualitative schemes, while the surrounding yellows go mainly in the basic sulfide section, with Zn and Cd as borderline cases. The orange includes the very dense platinum elements. 6) Some numbers for t,he predicted positions' of heavier elements are shown in the white rectangles a t the bottom. However, those under thef-elements should be designated as g-filling d,ams since 5 g should fill before 6 f. A' the April, 1969, ACS meeting, element 104, ekahafnium was reported synthesised by Seahorg and Ghiorso. They are focusing their next efforts on

110 and 114. Other magic number nuclides like 164 (with 196 neutrons) may Eoon be synthesized and may h w e half-lives permittingstiudy.

Choice of colors must be partially subjective owing to ambiguities of the electronegativities which can he affected by oxidation state and coordinat,ion number in some methods of calculation. Comparison of scales by Pauling, Allred-Rochow, and Rlulliken may be found in inorganic chemistry textbook^.^ I n doubtful, or borderline cases, chemical considerations determined the choice between two possible colors. The scale adopted here to reveal properties follows Eleelroncgativity speetwm (on a scale ranging from Fr -0.8 to F -4.0) Highly electropositive elements which form Blue: below 1 ionic compounds and very basic oxides. Electropositive elements farming both ionic Green: 1 to 1.4 and iovalent compounds. Yellow: 1.4 to 1.9 Intermediate element6 forming many covalent comoaunds. I : 1.9 l o 2.2 I n t t m t r d h r , rl~lnrntcfmninc mnlnl) cuvillcnt e~ I I > ~ I ~ I I I.*MI . ~ .ucidic micl~~Ilrd: ?li to :l.O ~ l ~ c l ~ oeIt~nm.t~ ~ ~ fdmil ~ ~ gl il . rvz ~~l i W ions and covalent compounds. Violet: above 3.0 Highly electronegative, the hydrogen-bondforming elements. ~

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To help interpret the photograph, we have: Green, Li, Mg, So, Y, Zr, Hf, Yellow, H, Be, Al, Orange, B, C, Si, P, Cu, etc. The only blues are Na-Fr, and Ca-Ra. There are but four reds, S,C1, Br, I, and but three violets (infrared), N, 0, and F. Discussions of where to put La and Lu below Y are. extensive. We mean only to suggest their chemical similarity, not that there are 15 f electrons. Had wall space permitted, these ,f-elements might better be placed below the d-elements. Cmstrudion Details: Primary color latex wall paints were obtained custom mixed for saturation of hue. Squares of 7'1% in. were painted on ahe&. plywood and the borders placed on them with 3/4-in. black Scot,ch tape. The letters have 2 in. capitals, and nnmerals are 1'1. in. made of '/,sin. paper board aveilable a t art and drafting supply stores in black and white. These were attached wit,h Elmer's Glue-All. These sizes are easily legible a t 50-ft distance.

MAZURS,E. G., "Types of Graphical Representations of the Periodic System of Chemical Elements," E. Masurs, 6 S. Madison Ave., I ~ d r e n g eIll., , 1957. J. W., JR.,J . CHXM. EDUC.,34,70 (1067). EICHINGER, a SANDRRSON, R. T., "Teaching Chemistry with Models," D. Van Nostrand, Prineet,on, N. J., 1962; J. CHBM.EDUC.,36, 'm7 11454) .*-,. \-"

' SEABORG,G.,

A N D BLOOM, J., Scientific American, 220, 56 (1969) (April). 'For example see: COTTON,F. A,, A N D WILKINSON,G., "Advanced Inorganic Chemistry,'' (2nd Ed.) Interscience (division of John Wiley & Sans, Inc.), New York, 1966, p. 103.

The periodic t a b l e on display in the lecture holl

Volume

47, Number 4, April 1970

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