THE PERIODIC TABLE OF THE CHEMICAL ELEMENTS.
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Hydrogen H = 1·008 | [a] | Hydrogen H = 1·008 | | |||||||||||||||||||||||||||
| | ||||||||||||||||||||||||||||||
| Helium He = 4·00 | Lithium Li = 6·94 | Glucinum Gl = 9·1 | Boron B = 10·9 | Carbon C = 12·005 | Nitrogen N = 14·008 | Oxygen O = 16·00 | Fluorine F = 19·0 | | ||||||||||||||||||||||
| Neon Ne = 20·2 | Sodium Na = 23·00 | Magnesium Mg = 24·32 | Aluminium Al = 27·1 | Silicon Si = 28·3 | Phosphorus P = 31·04 | Sulphur S = 32·06 | Chlorine Cl = 35·46 | | ||||||||||||||||||||||
| Argon A = 39·9 | Potassium[] K = 39·10 | Calcium Ca = 40·07 | Scandium Sc = 45·1 | Titanium Ti = 48·1 | Vanadium V = 51·0 | Chromium Cr = 52·0 | Manganese Mn = 54·93 |
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| Copper Cu = 63·57 | Zinc Zn = 65·37 | Gallium Ga = 70·1 | Germanium Ge = 72·5 | Arsenic As = 74·96 | Selenium Se = 79·2 | Bromine Br = 79·92 | | |||||||||||||||||||||||
| Krypton Kr = 82·92 | Rubidium Rb = 85·45 | Strontium Sr = 87·63 | Yttrium Y = 89·33 | Zirconium Zr = 90·6 | Columbium Cb = 93·1 | Molybdenum Mo = 96·0 | ? |
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| Silver Ag = 107·88 | Cadmium Cd = 112·40 | Indium In = 114·8 | Tin Sn = 118·7 | Antimony Sb = 120·2 | Tellurium Te = 127·5 | Iodine[d] I (or J) = 126·92 | | |||||||||||||||||||||||
| Xenon Xe = 130·2 | Cæsium Cs = 132·81 | Barium Ba = 137·37 | Lanthanum La = 139·0 | Cerium[e] Ce = 140·25 | ? | ? | ? | ? | ||||||||||||||||||||||
| ? | ? | ? | ? | ? | ? | ? | ? | ? | ||||||||||||||||||||||
| ? | ? | ? | ? | ? | Tantalum Ta = 181·5 | Tungsten W = 184·0 | ? |
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| Gold Au = 197·2 | Mercury Hg = 200·6 | Thallium Tl = 204·0 | Lead Pb = 207·20 | Bismuth Bi = 208·0 | Polonium (210) | ? | ||||||||||||||||||||||||
| Emanation (Niton) 222·0 | ? | Radium Ra = 226·0 | Actinium ? | Thorium Th = 232·15 | Ekatantalum ? | Uranium U = 238·2 | ? | ? | ||||||||||||||||||||||
There are several somewhat different forms of this Periodic Table. This is one of the simplest, but it lacks certain advantages of some of the more complicated forms. The atomic weights given are those of the International Atomic Weights Committee for 1920-1. They are calculated on the basis, Oxygen = 16. The number of decimal places given in each case indicates the degree of accuracy with which each atomic weight has been determined. The letter or letters underneath the name of each element is the symbol by which it is invariably designated by chemists.
The number above each column indicates the valency which the elements of each group exhibit towards oxygen. Many of the elements are exceptional in this respect.
[a]: The exact position of Hydrogen is in dispute.
[b]: The positions of Argon and Potassium have been inverted in order that these elements may fall in the right columns with the elements they resemble; [d]: so also have the positions of Tellurium and Iodine.
[c]: The whole of “Group 8” forms an exception to the Table.
[e]: There are a number of ill-defined rare earth metals with atomic weights lying between those of Cerium and Tantalum. They all appear to resemble the elements of “Group 3,” so that their positions in the Table cannot be decided with accuracy.
It is now some years since the late Sir William Crookes attempted to explain the periodicity of the properties of the elements on the theory that they have all been evolved by a conglomerating process from some primal stuff—the protyle—consisting of very small particles. He represented the action of this generative cause by means of a “figure of eight” spiral, along which the elements are placed at regular intervals, so that similar elements come underneath one another, as in Mendeléeff’s table, though the grouping differs in some respects. The slope of the curve is supposed to represent the decline of some factor (e.g., temperature) conditioning the process, which process is assumed to be of a recurrent nature, like the swing of a pendulum. After the completion of one swing (to keep to the illustration of a pendulum) whereby one series of elements is produced, owing to the decline of the above-mentioned factor, the same series of elements is not again the result as would otherwise be the case, but a somewhat different series is produced, each member of which resembles the corresponding member of the former series. Thus, if the first series contains, for example, helium, lithium, carbon, &c., the second series will contain instead, argon, potassium, titanium, &c. The whole theory, though highly interesting, is, however, by no means free from defects.
The Corpuscular Theory of Matter.
§ 79. We must now turn our attention to those recent views of the constitution of matter which originated to a great extent in the investigations of the passage of electricity through gases at very low pressures. It will be possible, however, on the present occasion, to give only the very briefest account of the subject; but a fuller treatment is rendered unnecessary by the fact that these and allied investigations and the theories to which they have given rise have been fully treated in several well-known works, by various authorities on the subject, which have appeared during the last few years.[95]
[95] We have found Prof. Harry Jones’ The Electrical Nature of Matter and Radioactivity (1906), Mr. Soddy’s Radioactivity (1904), and Mr. Whetham’s The Recent Development of Physical Science (1909) particularly interesting. Mention, of course, should also be made of the standard works of Prof. Sir J. J. Thomson and Prof. Rutherford.