Atomic structure

“ The study of the radio-active substances and of the discharge of electricity through gases has supplied very strong experimental evidence in support of the fundamental ideas of the existing atomic theory. It has also indicated that the atom itself is not the smallest unit of matter, but is a complicated structure made up of a number of smaller bodies. ”

“ While the discovery of the independent existence of the electron as a constituent of the structure of atoms gave a great impetus to the study of atomic structure, it was soon found that the removal or addition of an electron from an atom did not appear to cause a permanent transformation of the atom ”

“ Without entering into the difficult question of the actual distribution of the exterior electrons in any atom, it is obvious that the number and position of the outlying electrons of the atomic structure, which probably mainly influence the chemical and physical properties of the atom, are determined by the charge on the nucleus. ”

“ There is much that might indicate that, on the whole, it is impossible to obtain a consistent picture of atomic processes in space and time with the help of the motions of the nuclei and the electrons and the variations in the state of the ether, and with the application of such fundamental conceptions of physics as mass, electric charge and energy. ”

“ The leading historical stages in the evolution of the modern conception of the molecular structure of matter are treated in the following passage from James Clerk Maxwell’s article Atom in the 9th edition of the Ency. Brit.
“Atom [1] (ἄτομος) is a body which cannot be cut in two. The atomic theory is a theory of the constitution of bodies which asserts that they are made up of atoms. ”

“ This stratification, which previously seemed so incomprehensible, agrees exactly with the feature so fundamental in the atomic theory that a free electron cannot give energy under a certain quantum to an atom. We can imagine that, in the non-illuminated central space between the bright strata, the electrons each time under the influence of the outer electric field obtain the amount of kinetic energy which must serve to excite the atoms of the attenuated vapour. ”

“ In one form of a theory which has rendered great service to physical science—I mean Planck's theory of the 'quantum'—the changes from radiant to kinetic energy are supposed to occur not continuously, but by definite steps, as would inevitably be the case if the energy were atomic in structure. ”

“ The atomic structure of matter was well-known to the ancient Hindus. One of the six systems of Indian philosophy is Vaisesika, from the Sanskrit root visesas, “atomic individuality.” One of the foremost Vaisesika expounders was Aulukya, also called Kanada, “the atom- eater,” born about 2800 years ago. ”

“ Do they not also indicate that any alteration in the specific gravity of the atom would give rise to a new series of compounds, thus apparently producing a new element? Surely there is nothing irrational in the idea that the influences of heat or electricity, or of other powers of which as yet we know nothing, may be sufficient to effect such changes in the atomic constituents of this earth.
The combination of elementary atoms takes place under the influence of an unknown force which we are compelled to express by a figurative term, affinity. ”

“ How can an aggregation of atoms, having all their affinities satisfied, take any further part in chemical reactions? Seemingly such a molecule, whatever its physical properties, must be chemically inert, incapable of any atomic readjustments. And so in point of fact it is, so long as its component atoms cling to one another unremittingly. But this, it appears, is precisely what the atoms are little prone to do. It seems that they are fickle to the last degree in their individual attachments, and are as prone to break away from bondage as they are to enter into it. ”

“ We can produce a system which is still simpler than the ordinary hydrogen atom, for we can extract the electron from the atom and get merely the positive charge left: these positively charged hydrogen atoms exist in large numbers in the positive rays. ”

“ The nuclear charge of an element controls the number and distribution of the external electrons, so that the properties of an atom are defined by a whole number, representing its nuclear charge, and are only to a minor degree influenced by the mass or atomic weight of the atom. ”

“ We see that changes in the atom large enough to change the chemical character of the atom, i.e. to split an atom of one element up into different kinds of atoms, involve enormous transformations of energy; in fact the explosion of the atom in a few pounds of material might be sufficient to shatter a continent. We are living in the midst, nay, are made up of quiescent volcanoes ”

“ The amount of energy required to break up an atom has a very important bearing on the problem of splitting up the atom, in other words the transmutation of the elements by physical means. We know that the atoms of the radio-active elements break up spontaneously, and give rise to atoms of another kind. Thus radium emanation splits up into helium and radium A, and radium A again splits up. ”

“ Starting with the atom, we believe no longer that it is indivisible. Atoms are composed of thousands of ions, as they are called—really little electric charges. Again, you know that we have found that all the elements fall into groups. Each group has certain related atomic weights and properties which can be and have been predicted in advance of the discovery of missing elements in the group. ”

“ We can imagine the atomic nucleus as composed of a large number of primates of differing species, and perhaps with many primates of the same species, the whole association being such as to favour stability. An example of such an association is afforded by the association of a positive nucleus with negative electrons to obtain a neutral atom. ”

“ There you will see the atoms in the solution flowing towards the negative pole and depositing themselves in minute crystals upon the metallic surface, if the negative pole is a metal, and adhering with great pertinacity; the metallic crystals penetrate the crystalline surface of the substance to be plated in minute arms filling up the infinitesimal space, and the atoms in this process transfer their atomic motion in line with the electric force, and become arrested as in the primitive state when they formed the crystalline foundations of primitive earth. ”

“ We will, then, imagine a molecule magnified to the size of a billiard ball, and the atomic triplet magnified to the size of three marbles, in the triangular position, within that molecule, at its centre; unless acted upon by electricity, when the molecule, the billiard ball, becomes oblate, and the three atoms are ranged in a line within, unless broken up by the mighty force of vibratory action. Nature never gives us a vacuum ”

“ In the meanwhile, the primitive atomic theory, which has served as the scaffolding for the edifice of modern physics and chemistry, has been quietly dismissed. I cannot discover that any contemporary physicist or chemist believes in the real indivisibility of atoms, or in an interatomic matterless vacuum. 'Atoms' appear to be used as mere names for physico-chemical units which have not yet been subdivided, and 'molecules' for physico-chemical units which are aggregates of the former. ”

“ With such penetrating agents as Röntgen and cathode rays at our disposal, other properties which the atom retains unaltered have been brought to light, such, for example, as the absorption of these rays when they pass through atoms; the absorption by a given atom is quite independent of any other atoms with which it may happen to be associated, and depends only on the quality of the atom itself. ”

“ According to the view we have taken, atomicity corresponds to complexity of atomic arrangement, and the elements of high atomicity consist of more vortex rings than those whose atomicity is low.”
“Thus high atomicity corresponds to complicated atomic arrangement, and we should expect to find the spectra of bodies of low atomicity much simpler than those of high. This seems to be the case, for we find that the spectra of Sodium, Potassium, Lithium, Hydrogen, Chlorine, which are all monad elements, consist of comparatively few lines.” ”

“ Everything known before the discovery of radio-activity pointed to the view that an atom is indestructible, and this made it difficult to see how atoms could have a structure built out of smaller things, because, if they had, one would expect to find that the structure could be destroyed, just as a house can be knocked down and reduced to a heap of bricks. ”

“ When the chemical and physical properties of the elements were known to be periodic functions of their atomic weights, the idea of a common origin and common substance became much more credible. Differences in atomic weight and differences in properties alike might reasonably be explained by the differences in the amount of the primordial substance present in the various atoms; an atom of oxygen being supposed to be composed of sixteen times as much stuff as the atom of hydrogen, but to be made of the same ultimate material. ”

“ When the missing atomic weight 0.0302 is multiplied by the square of the velocity of light according to Einstein’s theory, it is found to represent a tremendous amount of energy. Indeed, the energy released in forming a helium nucleus from two protons and two neutrons turns out to be seven million times that released when a carbon atom combines with an oxygen molecule to produce a molecule of carbon dioxide in the familiar process of combustion. ”

“ During the Middle Ages the desire to find a way to convert a base metal like lead into gold was the outstanding incentive for research in chemistry. When the important role of the nucleus in determining the chemical properties of an atom became clear and the natural transmutation accompanying 11 radioactivity was understood, the fascinating idea occurred to many people that perhaps man would soon be able to alter the nucleus of a stable atom and thus deliberately convert one element into another. ”

“ The number of recoil particles increases with the atomic weight of the metal. Comparing experiment with theory, the central charge in an atom corresponds to about one-half the atomic weight multiplied by the charge on an electron, or, as it is expressed, 1⁄2 Ae.
There is only one lighter atom than helium, namely, hydrogen, which has a mass only one-fourth as great. [Pg 40] When alpha particles are discharged into hydrogen, a few of the latter atoms are found to be propelled to a distance four times as great as that reached by the alpha particles. ”

“ Here we had the first direct evidence (1) that an atom is a complex structure, and (2) that electrical charges enter into its make-up. With this discovery, due directly to the use of the new agency, X-rays, the atom as an ultimate, indivisible thing was gone, and the era of the study of the constituents of the atom began. ”

“ An adequate theory of material phenomena is necessarily ultimately atomic. The older mathematical type of atomic theory which regards the atoms of matter as acting on each other from a distance by means of forces whose laws and relations are gradually evolved by observation and experiment, is in the present method expanded end elucidated by the introduction of a medium through whose intervention these actions between the material atoms take place. ”

“ We have seen that the view, so strongly supported by recent experiments, that the atoms of the elements are aggregations of simpler systems, involves the admission that losses or gains of mass or weight must occur in the formation of the heavier atoms. But we know that the ratio of mass to weight is the same for all substances, from hydrogen, the lightest, up to uranium, the heaviest, and even, as Southern's experiments on uranium and my own on radium have shown, for radio-active substances. ”

“ To make room for these we have to remember that the atomic nucleus has remained entirely undefined and beyond our problem; so that what may occur, say when two molecules come into close relations, is outside physical science—not, however, altogether outside, for we know that when the vital nexus in any portion of matter is dissolved, the atoms will remain, in their number, and their atmospheres, and all inorganic relations, as they were before vitality supervened. ”

“ The magnitude of the molecule, as compared to the inter-atom, is about on the same ratio as a billiard ball to a grain of sand; the billiard ball being the domain wherein the triple inter-molecules rotate, the inter-molecules again being the field wherein the atomic triplets sympathetically act, and again progressively, in the inter-atomic field, the first order of the etheric triplets begins to show its sympathetic inreach for the centres of neutral focalization. It is impossible for the imagination to grasp such a position. ”