What is an element? - Journal of Chemical Education (ACS Publications)


S. Weiner. J. Chem. Educ. , 1941, 18 (6), p 296. DOI: 10.1021/ed018p296.2. Publication Date: June 1941. Cite this:J. Chem. Educ. 18, 6, 296-. Note: In...
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LETTERS Good and Bad??? What Is an Element? T o the Editor: To the Editor: The "Gleanings from a Conference" in the March The point raised by E. C. Payne [J. CAEM.EDUC., issue of the JOURNAL OF CHEMICAL EDUCATION are 18, 195 (April, 1941)], namely that the term "chemical broadly significant to teachers of high-school chem- element" needs redefinition in view of our long acistry. May I comment b r i d y on one of these state- quaintance with atomic disintegration, both sponments, namely: "There is reported a general lack of taneous and "artificial," is worthy of study. Howability to think, and an overemphasis on memory of ever, his proposed definition of an element as a subquestions and answers." Of all the teaching devices stance of the second (or third) order of complexity is not in use, the question and answer method is the most uni- a definition, but rather a classification. Moreover, versally used. Other methods, such as the lecture, lec- it refers more properly to the atom than to the element. ture demonstration, and group and individual labPerhaps a more explicit definition might be as foloratory work have their place, hut even in these the lows: A chemical element is a pure substance to which, question and answer technic is important. Testing when it is isolated and purified, each and all of the folprograms quite generally employ this technic. lowing statements apply: .. 1. When subjected to.electron or X-ray diffraction in the Good questions and good answers cannot be overemphasized, if the question is the "psychological solid stat< its lattice is shown to contain but one type of positively charged particle, though this particle may exist in groups basis" of all learning. In a classification of good and relatively widely separated from other groups, and though bad questions, from the standpoint of emphasis, I ncgativc parlirlrs (clcctrons' may also exist in the larricr would include among the former, thought questions, 2. When wbjected to electron t,ornbardmtnt. ~t emits only and among the latter, qu&ions of recall. For ex- a single sct of rhe normal K and I, lines ch:mcteristi,,of elements. ample, questions on the topic of fuels, previously as- If i t decomposes, wholly or partidly, to form one or more other substances or materials, the total resulting material emits under signed, such as. Define a fuel, dBes a fuel give energy, electron bombardment one or more new sets of K and L lines and name the solid, liquid, and gaseous fuels, can be 3. The atomic number as deduced from its K and L radiaoveremphasized. Memory is tested. The purpose is tions by Moseley's law gives i t a place in the periodic table that to find out if the pupil got his lesson, and the price is corresponds t o the properties it shows in its combinations (or to combine) with other elements. approval or disapproval of the teacher. Such approval failure 4. Its constituent partides have a dense positively charged may become the goal rather than chemistry. nucleus, whose charge is p?oportional t o the atomic number, On the other hand, a question such as: Is electricity and a relatively less dense, completely negative atmosphere a fuel, provokes debate and leads to research. To ("shell"). 5 . When excited thermally i t emits a characteristic line answer this question a student must learn something spectrum, peculiarly its own, which is independent of the past about electricity, energy, and fuels, both solid and history of the sample but may vary according to the method fluid. It is a thought question. and conditions of excitation. The spectrum may exhibit rotaWould it not be profitable, particularly to us of your tional or vibrational bands a t low temperatures of excitation or readers who are teaching high-school chemistry, to in absorption spectra, but a t temperatures so high that electronic spectra are observed, the spectral lines cannot be analyzed include in your columns a sample list of good and bad line as belonging to the spectra of two or more other elements, nor questions in chemistry from the standpoint of em- can the spectral terms be divided into sets each belonging to a phasis, different (other) element. GEORGEW. FOWLER 6. Each of its constituent particles is sometimes electrically neutral and sometimes electrically charged, though it may happen that one of these states is the normal condition and the other is attained only by the expenditure of considerable energy.

Since item 4 in the above is based on the ultimate structure of the atom and is therefore hypothetical rather than empirical, it may perhaps be omitted. S. WEINER 2fi30 NORTH53nn STREET MILWAUKEE, WISCONSIN

We are reminded of the fact that some thirty years ago the British Association was urged to offer a prize of a thousand pounds to anyone tvho could completely and satisfactorily define an element within the comprehension of the layman. It seemed then-and still seems-that one must know what an element is in order to understand its definition.-&.

'The First High-School Chemistry Laboratory? To the Editor: There recently came to my attention a letter in the .April, 1941, issue of the JOURNAL having the caption: "A Chemical Pioneer in High-School Teaching." In this letter, Dr. Brandt V. B. Dixon is quoted as having claimed that a high-school laboratory installed by him in the Central High School of St. Louis in September, 1876, was as far as he could learn the first high-school chemical laboratory in the United States. We desire to lay claim to a much earlier date for the establishment of a high-school chemical laboratory in this country. This was a t the Central High School of Philadelphia, an institution that recently celebrated its one-hundredth anniversary, having been founded in 1838, the oldest public high school outside of New England. To support our contention, we quote from the "History of the Central High School of Philadelphia," by Franklin Spencer Edmonds, published by Lippincott in 1901. Martin H. Boy6 became professor of chemistry in 1851. "Provision was made for a laboratory which was fitted up in the basement, and illustrative apparatus was provided. From this time, therefore, chemistry assumed its proper place in the cur~iculum."-Page 113. I n 1862 during the incumbency of Dr. B. P w a r d Rand in the chair of chemistry (he had succeeded Professor Boy6 in 18591, John Kingsbury, formerly Superintendent of Schools in Rhode Island, visited the Central High School of Philadelphia and reported: "We were particularly pleased with the chemical laboratory, not with the room, or with the chemicals, or apparatus, but with the unmistakable evidence that there was work done there.. . .We were informed that the chemicals were p u t into the hands of the pupils and they are taught to perform t h e experiments themselves."-Page 179.

Reference could also be made to the laboratory work done in chemistry during the professorship of the renowned Elihu Thomson (1870-80). However, the previous citations make it clear that chemical laboratory instruction started as early as 1831 and certainly was in full operation in 1862. We know that Dr. Dixon will be glad to accept this correction in order that the record may be entirely straight. ROBERT W. KUNZIG CENTRAL H~onScaoo~ PHILADELPHIA, PENNSYLVANIA

Paper for Platinum in Flame Tests

To the Editor: In these days of another national emergency our available supply of platinum again becomes a cogent issue. An examination of the current texts on qualitative analysis reveals that their authors seemingly are unacquainted with the method developed by Ehringhaus (Cent. Min., 1919, 192, also Annual Reports, Chemical Society, Val. XVII, 130) in which paper is substituted for platinum in flame-test technic. My experience with this test, following the procedure described in J. Ind. Eng. Chem., 12, No. 5, 500 (May, 1920) long ago led me permanently to discard platinum for this purpose. Platinum has little, if any, advantage over paper; hence to use the former in this way seems to me to be an unnecessary waste of an important and valuable material. Several methods have been devised for making bead tests without platinum wire. Small quartz or glass rods and lead-pencil leads serve fpr borax beads. Little, but very beaufiful beads can.be made with microcosmic salt as follows: Strips of filter paper, approximately one cm, by 10 cm., are soaked in a hot saturated solution of the salt, dried, and the process repeated until crystals show on the surface of the paper. For the test place a drop of the test .solution (Co, Ni, or Mn salt) on one end of the prepared strip and hold it in the outer edge of a Meker flame until the paper has carbonized to a depth of 5-10 mm. A hand magnifier will show a number of well formed and characteristic beads on the carbonized edge.

The surface tension of fused borax is such that it cannot be used in this method. C. C. KIPLINGER W s s r LIBERTY STATETEACHERS COLLEGE WESTLIBERTY, WESTVIRGINIA