IT has been found difficult to give the elements argon and helium (and I think the same difficulty will exist in respect to the gas krypton) their proper place in the scheme of arrangement of the elements which we owe to the ingenuity and scientific acumen of Newlands, Mendeleef and others. Some years ago, carrying a little further Professor Emerson Reynolds' idea of representing the scheme of elements by a zigzag line, I thought of projecting a scheme in three dimensional space, and exhibited at one of the meetings of the Chemical Society t a model illustrating my views. Since that time I have rearranged the positions then assigned to some of the less known elements in accord ance with later atomic weight determinations, and thereby made the curve more symmetrical. Many of the elemental facts can be well explained by supposing the space projection of the scheme of elements to be a spiral. This curve is, however, inadmissible, inasmuch as the curve has to pass through a point neutral as to electricity and chemical energy twice in each cycle. We must, therefore, adoptions other figure. A figure of eight will foreshorten into a zigzag as well as a spiral, and it fulfills every condition of the problem. Such a figure will result from three very simple simultaneous motions. First, an oscillation to and fro (suppose east and west): secondly, an oscillation at right angles to the former (suppose north and south); and thirdly, a motion at right angles to these two (suppose downward), which, in its simplest form, would be with unvarying velocity. I take any arbitrary and convenient figure of eight, without reference to its exact nature; I divide each of the loops into eight equal parts, and then drop from these points ordinates corresponding to the atomic weights of the first cycle of elements. I have here a model representing this figure projecteg in space; in it the elements are supposed to folloW'”6ne another at equal distances along the figure of “eight spiral, a gap of one division being left at the point of crossing. The vertical height is divided into 240 equal parts, on which the atomic weights are plotted, from H = 1 to Ur = 239'59. Each black disk represents an element, and is accurately on a level with its atomic weight on the vertical scale. The accompanying” figure, photographed from the solid' model, illustrates the proposed arrangement. The elements falling one under the other along each of the vertical ordinates are shown in the table: H He Li Gl B C N o CI Ar K Ca Sc Ti V Cr Br Kr Rb Sr Yt Zr Nb Mo I — Cs Ba La Ce ( ) ( ) ( ) — ( ) ( ) ( ) ( ) Ta W Th — Ur Mn Fe'Ni'Co Rh'Ru'Pd ( ) IrPt'Os Na Mg Al Si P S Cu Zn Ga Ge As Se Ag Cd In Sn Sb Te ( ) ( ) ( ) ( ) ( ) ( ) An Hg TI Pb Bi — The bracketed spaces between cerium and tantalum are probably occupied by elements of the didymium and erbium groups. Their chemical properties are not known with sufficient accuracy to enable their positions to be well defined. They all give colored absorption spectra and have atomic weights between these limits. Positions marked by a dash (—) are waiting for future discoveries to fill up. Let me suppose that at the birth of the elements, as we now know them, the action of the vis generatrix might be diagrammatically represented by a journey to and fro in cycles along a figure of eight path, while simultaneously time is flowing on, and some circumstance by which the element-forming cause is conditioned (e. g., temperature) is declining (variations which I have endeavored to represent by the downward slope). The result of the first cycle may be represented in the diagram by supposing that the unknown formative cause has scattered along its journey the groupings now called hydrogen, lithium, glucinuiii, boron, carbon, nitrogen, oxygen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, sulphur, and chlorine. But the swing of the pendulum is not arrested at the end of the first round. It still proceeds on its journey, and, had the conditions remained constant, the next elementary grouping generated would again be lithium, and the original cycle would eternally reappear, producing again and again the same fourteen elements. But the conditions are not quite the same. Those represented by the two mutually rectangular horizontal components of the motion (say chemical and electrical energy) are not materially modified; that to which the vertical component corresponds has lessened, and so, instead of lithium being repeated by lithium, the groupings which form the commencement of the second cycle are not lithium, but its lineal descendant, potassium. It is seen that each coil of the lemniscate track crosses the neutral line at lower and lower points. This line is neutral as to electricity and neutral as to chemical action. Electro-positive elements are generated on the northerly or retreating half of the swing, and electro-negative elements on the southerly or approaching half. Chemical atomicity is governed by distance from the central point of neutrality; mon- atomic elements being one remove from it, diatomic elements two removes, and so on. Paramagnetic elements congregate to the left of the neutral line, and diamagnetic elements to the right. With few exceptions, all the most metallic elements lie on the north. Till recently chemists knew no element which had not more or less marked chemical properties, but now, by the researches of Lord Rayleigh and Prof. Ramsay, we are brought face to face with a group of bodies with apparently no chemical properties, forming an exception to the other chemical elements. I venture to suggest that these elements, helium, argon, and krypton, in this scheme naturally fall into their places as they stand on the neutral line. Helium, with an atomic weight of four, fits into the neutral position between hydrogen and lithium. Argon, with an atomic weight of about forty, as naturally falls into the neutral position between chlorine and potassium. While krypton, with an atomic weight of about eighty, will find a place between bromine and rubidium. See how well the analogous elements follow one another in order: C, Ti, and Zr; N and V; GI, Ca, Sr, and Ba; Li, K, Rb, ana Cs; CI, Br, and I; S, Se, and Te; Mg, Zn, Cd, and Hg; P, As., Sb, and Bi; AI, Ga, In, and Tl. The symmetry of these series shows i.hat we are on the right track. It also shows how many missing elements a.re waiting for discovery, and it would not now be impossible to emulate the brilliant feat of Mendeleef in the celebrated cases of Elm-silicon and Eka-aluminum. Along the neutral line alone are places for many more bodies, which will probably increase in density and atomic weight until we come to inert bodies in the solid form. Four groups are seen under one another, each consisting of closely allied elements which Prof. Mendeleef has relegated to his eighth family. They congregate round the atomic weight 57, manganese, iron, nickel, and cobalt; round the atomic weightlOil, ruthenium, rhodium, and palladium; while lower down round atomic weight 105 are congregated osmium, iridium, and platinum. These groups are inter- periodic because their atomic weights exclude them from the small periods into which the other elements fall, and because their chemical rclations with some members of the neighboring groups show that they are interperioilic in the sense of being formed in transition stages. Note, June 22, 1898.—Since the above was written, Prof. Ramsay and Mr. Travers have discovered two other inert gases accompanying argon ill the atmosphere. These are called neon and inetargon. From data supplied me by Prof. Ramsay, it is probable that neon has an atomic weight of about 22, which would bring it. into the neutral position between fluorine and sodium. Metargon is said to have an atomic weight of about 40; if so, it shares the third neutral position with argon. I have marked the positions of these new elements on the diagram.—Chemical News.
This article was originally published with the title "On the Position of Helium, Argon, and Krypton in the Scheme of Elements" in s , , 18948 (December 2012)