mnething new from the p o ~ t Chemical Periodicity This feature column is now in its third annual cycle. In keepine with the intention of presenting articles that deal with this writer topics &rently being taught in the urges you, the reader, to refer to the Octoher 1980 and October for the references already ah1981 issues of THIS JOURNAL stracted for use. The maior theme for this month is chemical periodicity and a smail repertory of short anecdotes for classroom use. Mendeleev is credited with developing and charting the ideas of periodicity of chemical and physical properties of elements. In the October 1980 issue of J. CHEMEDUC,p. 730, I referred to the "American Forerunners of Periodic Law," by George Kauffman. T h e teacher of beginning chemistry must recognize that of all of those attempting t o discover and oreaniie the relationshin between the elements. i t was Mendereev who showed the r&tionships and was able to use his chart to predict new elements leading to the comprehension of the natural law.
assr rooms,
"The first attempt which was made in this direction was the following: I chase substances of the smallest atomic weight and arranged them in the order of the value of their atomic weights. From this it appeared that there seemed to be a periodicity in the properties of the individual substances, and indeed that, if one considered the valences, one element followed the other in the arithmetical sequence of their atomic weights." (The quotation is from Journal of the Russian Chemical Society, 1, 1969.) J. CHEM. EDUC., 46, 135 (1969). "Great Moments in Chemistry, Part X, Search for the Elements," Ferenc Szabadvary, CHEMISTRY, 46, 14-16 (1973). Szahadvary's article was written in the form of a dialog between a science writer and a professor as they discuss how same of the elements were discovered and named. The trends in naming the elements is most interesting. "The Periodic Law," W. A. E. McBryde, CHEM 13NEWS, 2-3 (February 1974). Here is another series of short vignettes concerning the history and people involved in the development of the periodic law. The main lesson that the teacher can learn is that in science, versus the arts, more than one person can and usually is working on the same idea-an important point to present to beginning students. This, however, is not the care in the arts; only Beethoven eould have written the Emica Symphony. McBryde's article is "a glimpse behind the scenes of the less visible parts of the total story." The discovery of Element 101, Mendeleevium, is documented by a simed strip chart shown on the front cover of the January 1959 &sue of THIS JOURNAL. An excellent account of the -~ events that occurred as that chart was being made appears in the texthook "CHEMISTRY." bv ChoDDin. .. . Summerlin, and Jaffe, Silver Burdett company, hiorristown, NJ, 1978,~:516. ChoDDin .. was.. bv.the wav.".a member of the discoverinn team. Couple the story with the chart and you have a n excellent anecdote for inclusion in lessons on the periodic tahle of the elements. ~
~~~
JOSEPH
Edited by: S. SCHMUCKLER
Chairman of Science Education Temple University 345 Riner Hall Philadelphia,PA 19122
"Some Recollections of Early Nuclear Age Chemistry," Glenn T. Seaborg, J. CHEM. EDUC.,45,278-289 (1968). "Since we can think of the nuclear age as relating to the nuclear fission of uranium, my admittedly incomplete recollections will be concerned with the work on the nuclear fission of uranium and some of the work leading to this, as well as some of the work following the discovery of the nuclear fission reaction. This was all related to the periodic table and attempts to extend the periodic tahle beginning before World War 11. The work can he considered to hegin with the search for the transuranium elements, that is, efforts to extend the Periodic Table beyond uranium." Thus wrote Dr. Seaborg in what might beralled an "oral historv" written hv one of the key participants. The article is complete with ;harts, nuclear equations, and photographs of the d o n e e n of the modern nuclear age. Seaborg describes how he announced to the world the discovery of two new elements on the famous "Quiz Kids" radio program on November 11, 1945. Throughout the article one can almost feel as though he were listening fmthand as Seaborg recounts the events of the work involved from pre- to post-World War 11. At one point he tells his student interviewer: "Oh yes, Dick. Recently there have heen the new elements discovered-lements with atomic numhers 95 and 96 out at the Metallurgical Laboratory here in Chicago. So now you'll have to tell your teachers to change the 92 elements in your schoolbook to 96 elements." Dr. Seaborg later says, "As a result of that broadcast, in which I told the audience that there were 96 elements instead of 92, I received a number of letters from school children whosaid that thev had told their teachers this as I had asked them to do, hut their teachers had not believed them. They asked me to hail them out of the trouble that I had gotten them into; I tried my best to do so by writing them eonfirming letters that they could show their teachers." ~~~~~~~~
~
~
T h e very human side of this great scientist is most evident.
"A New Periodic Chart, With Electronegativities," R. T. Sanderson, J. CHEM. EDUC., 33,443445 (1956). The idea of representing physical (and other related) properties of atoms by using discs of varying radii in a periodic table began with Sanderson. One need only to lmk in mast current chemistry texts and somewhere within that text will be aperiodic chart using Sanderson's discs. The purpose of including this article here is to remind readers that "visual aids" properly designed and used are still excellent teachine tools. Sanderem's art& dearrihes the runvtruction of a periodic tnhle with wrying sized dircr t u rhuw relnrive differences in electrunegativiries of the elements He drrrribrs constnrctlon details and ruggmm a color coding as well. ~~~
~
~
This feature Includesannotations of articles from previous issues of TK JWRNAL and omer science teaching journals. Topics will be pre-
sented in the issue prim to the time when the topic is taught in a ?p-,i cal high S C ~ O O C I~ r r i c ~ I u m .
Volume 59
Number 11
November 1982
961
"Models for Demonstrating Electronegativity and Partial Charge," R. T. Sanderson, J. CHEM. EDUC.,36,507-512,
(1959). The "Chem and Bond Approach,, curricula in. and utilized plastic molded spheres to represent atoms and ions. As mentioned above, Sanderson was one of the people who propounded this teaching technique. In this paper, Sanderson reports: "The instructional usefulness of extending the concept of eleetronegativity to the estimation of partial charges on combined atoms has been discussed in a series of earlier papers in THIS JOURNAL U , 2 , 3 , 4).There have also appeared descriptionsof a periodic chart showing atomic electronegativities by color (5)and of two-dimensional representations of molecules showing partial charge by color (6).One purpose of this paper is to report the extension of these applications of color to models which now permit in three dimensions a new visu-
962
Journal of Chemical Education
alization. A second purpose is to re-emphasize on the basis of continuing experience, the unique teaching value of such models and of the fundamental principles which they dramatize." This paper is one of the most complete on giving construction information of models and detailed information on their act u a l u s e in the classroom. "Valence: A Laboratory Exercise for General Chemistry," R. T. Sanderson, J. CHEM. EDUC.,37,261 (1960). This is an excellent exercise using easily constructed models from plastic spheres that allows the studenta tovisualize and discover ''the for, and results of, =hemid bond The exercise also gives appreciation of the of the eledronic similarities the classification of the chemical elements into groups of the table.m
