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| Topic: Dr. Abram's Electron Theory
by
William F. Hudgings Section: Part VII, Empty Space in Atoms Table of Contents to this Topic |
| MUCH EMPTY SPACE IN ATOMS If the diameter of an atom of hydrogen is 10-8 cm. and it is composed of only one proton and one electron, each of which has a diameter of only 2 x 10-13 cm. how is its bulk made up, seeing that the two electrons, even if laid side by side would have a combined diameter which would be insignificant in comparison to the diameter of the atom which they form? The only conclusion to be reached is that the negative electron revolves around its proton nucleus at a distance, just as the moon revolves around the earth 240,000 miles away; or else the two revolve around each other in dumbbell in fashion at relatively great distances apart. Thus the greater portion of the bulk of the atom consists of empty space. Various experiments corroborate the conclusion that the negative electrons in all atoms revolve about their positive nucleus at considerable distances therefrom, and from each other, even as the planets of our solar system have large orbits about the sun. The proof that the one electron and one proton which compose the hydrogen atom, for instance, are not welded together into one united solid sphere, rests not merely upon the mathematical variance between electronic and atomic sizes, but upon the hydrogen spectrum in the spectroscope which indicates an orbital motion on the part of the electrons of the atom. When an electron and a proton do combine into one granule, however, experiments have shown that they then, in their united state, actually occupy a space eight tenths of one percent smaller than either did originally! Prof. Aston has demonstrated that even two protons and one electron may have a combined size which is smaller than one electron alone. Here is a real paradox in nature. An explanation which has been offered is that an individual isolated electron or proton suffers internal repulsion between its parts (if it may be said to have parts), thereby swelling its size; but when the two come in contact their spontaneous attraction for each other is so intense that they immediately merge into the closest possible union, there being no longer any repulsive swell in either particle because each has found its complement. Thus the two united can occupy a smaller space than either of them did in its individual, unsatisfied condition. It is the inertia of the electron and proton in the hydrogen atom that keeps them apart. For the same reason the moon does not fall upon the earth , nor the earth upon the sun, although there is strong mutual attraction. The size of any atom is marked by the orbit of its outermost electron, just as the size of our solar system is determined by the orbit of our distant sister Neptune. Now a comet may pass through our solar system without colliding with any planet in it, traveling through free space between the planets. But if the comet continues its journey through a vast number of solar systems the chances are that sooner or later it would find some planet in its path and a collision would result, unless a guiding Providenced. If the comet were larger than the planet which it struck, or if it were moving at an enormous velocity, it would either knock the obstructing planet to one side or else it would drive it on ahead as it continues its journey through the heavens. The comet might thus collide with several planets before its energy was sufficiently expended to cause its own deflection and ultimate stoppage. In a similar manner the gaseous atoms in a testing tube may be subjected to bombardment of electrons (cathode rays or beta rays) or by alpha particles, in which event it is found that some of the atomic systems suffer collision while others escape unharmed by reason of the flying particles passing successfully through the open spaces between the planetary electrons. When a collision occurs in any atomic system, that system is immediately charged, because the bombarding particles have deprived it of one of its satellites, or else has struck the nucleus and knocked out some protons. If an electron is struck, the atom is then deficient in negative electricity by one electron and is said to be charged positively. But if the nucleus is struck, and protons are thrown out, then the atom is charged negatively. In either event the wrecked atom is called an ion, and their presence is experimentally discernible. The path of the alpha or beta particles may be traced through the gas, and the collisions made visible by introducing water vapor into the tub and noting the points of condensation. It is simply a variation of the Thomson/Wilson cloud experiment already described. Every atom is ionized becomes a nucleus for a small drop of water, whereas the atoms which escape collision will not cause any condensation. The water globules are easily discernible. If alpha particles are shot through the gas, the resulting globules are so numerous that they appear as white streaks throughout the length of the tube. If the tube is sufficiently long the white streaks suddenly stop before the end of the tube is reached, thus indicating that the alpha particles have spent their energy and are unable to travel further through the gaseous atoms. If beta or cathode rays are used for the bombardment a very different effect is observed. Instead of there being a continuous streak of drops throughout the length of the tube only an occasional drop of water is formed. This shows that the beta particles are much smaller than the alpha particles, because they are able to pass through more of the atomic systems without colliding with anything. Alpha particles, as already mentioned, are aggregations of protons and electrons, whereas beta rays consist of individual electrons. While the former do not possess the enormous velocity of the latter, nevertheless they are capable of ionizing millions of molecules in each centimeter of their path and are rarely deflected from a straight line until their energy becomes largely spent near the end of their course. The beta particles, on the contrary, ionize only about one mercury molecule in 10,000. Their size is so minute that they can pass through the free spaces in that number of systems without striking any obstruction. In ordinary air they will ionize on an average about one molecule in every four inches, or the equivalent of one collision in each 100,000,000 molecules. It is not surprising, therefore, that ordinary solids, like metal sheets, appear porous before these infinitesimal particles. And no better proof than this could be had of the enormous relative spaces existing between electrons within the atom. Spectrum analysis has contributed much to our present knowledge of electrons, particularly concerning their orbital motion in the atomic systems. The spectroscope, as the reader probably knows, consists in its simplest form of two telescopic lenses placed on opposite sides of a glass prism, together with a screen or photographic plate upon which the light under examination may fall. When light rays from any substance pass through the first lens they emerge parallel and thus pass into the triangular prism. When they emerge from the prism, however, they are broken up or separated according to frequency so that each wave length takes a different direction, being spread out like a wedge upon the spectral screen. Every line upon the screen or plate has its meaning, and spectrum analysis has become one of the most fruitful fields of physical research. The spectral lines are manifestly due to the frequency of rotation of the planetary electrons in the atoms under examination. If this is so, then any change in their rate of rotation should cause a shifting of these lines to a slightly different position on the screen. But how can the frequency of their rotation be affected? This can be done by the introduction of a magnetic field near the radiating substance. Its lines interweaving with the circular currents of the revolving electrons of the substance should either increase or retard their orbital frequency. The experiment was early undertaken by Larmor with unsatisfactory results; but in 1897 Prof. Zeeman of Amsterdam succeeded in demonstrating that a strong electromagnet does produce a definite shift of the spectral lines, thereby establishing the revolving state of electrons within the atom. We might hastily conclude that the immediate effect of a strong magnet would be to overpower the revolving electrons, or at least to cause their orbits to face round parallel to the lines of force instead of maintaining their accustomed positions. But experiments prove otherwise, the only perceptible effect being a slight change in velocity. No doubt the tendency of these circular currents is to adjust themselves normal to the magnetic lines of force; but they are prevented from actually doing so because of their great inertia, just as the inertia of a spinning top is able to resist the influence of gravity. The constant tendency of the top is to fall over, but so long as it is spinning at the proper speed it will defy gravitation sufficiently to remain erect. As soon as friction reduces the speed, however, the top yields more and more to gravity's force, resulting in a wobbling motion until eventually its inertia is overpowered completely and it falls motionless to the floor. But neither gravity nor any known magnetic or electrostatic field can compel the electrons of any atom to come to a standstill. This proves their velocity and inertia to be enormous. The spectroscope thus confirms the previously calculated inertia of electrons as determined from the Thomson/Wilson cloud experiment already described. Every frequency of rotation will produce its definite line in the spectrum. Planetary electrons may revolve many billions of times per second without impairing the stability of the atom, although there is, of course, a limit beyond which all atoms would radiate themselves to destruction. Theoretically, an aggregation of electrons would produce a red glow if they traverse their orbits at a speed of 400 billion times per second, and light of higher refrangibility would be emitted for velocities in excess of that. Obviously, therefore, the electrons in a normal atom do not possess such velocities as this, nevertheless their frequency of rotation is enormous when compared with any man-made machine. The armature of the highest speed modern type motor revolves less than fifty times a second. Electrons revolving even one billion times a second would thus rotate twenty million times faster than the most rapid electric motor. It is this enormous rotating motion of the electrons in the atom that gives the expelled particles of radioactive substances their exceedingly high velocities. We have already mentioned that alpha particles emitted by radium, polonium, etc., if permitted to fall upon a target covered with zinc-sulphide, will produce luminous flashes which are plainly visible through a small telescope. Inasmuch as the mass, velocity and inertia of these particles are known, it is therefore possible to compute the amount of power that is generated when they are suddenly stopped. If the stoppage is sufficiently quick, say within the diameter of a molecule, there is actually involved the expenditure of nearly 80 horse-power for an exceedingly minute fraction of time. There can be little doubt but that a way will eventually be found to harness some of the enormous energy now locked within the atoms of particles of matter around us, making it generally available for the benefits of humanity. WHY ATOMS DIFFER We have now considered experimental evidence: (1) that atoms are composed of aggregations of minute particles known as electrons; (2) that some are negative and some are positive (the latter being called protons) (3) that they have definite size with determinable mass, inertia and charge; (4) that there is no characteristic difference between the electron (or protons) of one type of atom and those of any other type; (5) that some of the electrons of atoms rotate in planetary fashion around a central nucleus at enormous velocities; (6) that there are great spaces between the planetary electrons in all atomic systems, similar to the arrangement of the planets of a solar system. These established facts bring us to the consideration of the precise arrangement of the electronic orbits of the various atoms and of the elemental difference between the ninety-two types of atoms known to science. The Rutherford-Soddy atomic models have lately been improved by Prof. Bohr, who was awarded the 1922 Nobel Prize in Physics by the Swedish Academy of Sciences (Einstein having received this prize for the preceding year). We shall accordingly endeavor to follow the reasoning of these eminent physicists and see how their theoretical structures account for known phenomena. If electrons revolve there must be some stabilizing force that holds them in bounds. There is no reason for supposing that their infinitesimal size works a reversal in the tried and proven laws of electromagnetics; therefore any and all atomic systems must be so arranged as to neutralize the characteristic repulsion of one electron for another of the same sign. How, then, does an atom hold itself together? The reasonable conclusion is that each atom must have a central nucleus which is of opposite charge to that of the electrons which rotate around it and having sufficient attractive power to hold all the orbital electrons in bounds even as our sun holds in check the various planets which revolve around it. This would necessitate there being at least as many protons in the nucleus as there are planetary electrons. The nucleus, however, could not consist entirely of protons; for positive charges are mutually repulsive even as negative charges are mutually repulsive. Hence the nucleus would be unstable if it were composed of protons alone. The Rutherford-Soddy atomic model, therefore, proposes that the nucleus of an atom consists of both positive and negative electrons, but not in equal number, probably arranged in blocks of four protons, with two negative electrons on each side as a binder. This would make the nucleus stable and would always result in an excess of protons for the purpose of stabilizing the remainder of the atom. The foregoing deduction has been confirmed by experiment. As early as 1911 Prof. Rutherford succeeded in isolating the nucleus of an atom and ascertained the number of elemental charges which it carried. This he found to be in each case approximately equal to half the atomic weight. He first determined the mass of an alpha particle, which turned out to be identical with that of the helium atom minus two elemental negative charges. Helium is the second lightest atom known and, as will be seen presently, it has two planetary electrons. The alpha particle is therefore one and the same thing as the nucleus of the helium atom with the two revolving electrons missing. If alpha rays from radium are intermingled with ordinary electric sparks the spectrum will show helium lines in the discharge path, although no such lines are observed before the discharge is subjected to the radium emanations. Now if these alpha particles (helium nuclei) are permitted to bombard the nuclei of other types of atoms thus ionizing them and causing them to condense vapor in the manner heretofore described, they may be deflected by a magnet of known strength; and from the amount of their deflection the quantitative charge on these nuclei may be calculated. The experiment was repeated for various types of atoms and the respective results compared. Moseley, in 1914, shortly before his untimely death in the world war, fully corroborated Rutherford's findings as to the character of the nuclei of various atomic types, although he followed an entirely different experimental method. His results are believed to be very accurate and are relied upon by chemists for the establishment of atomic weights. With the exception of hydrogen, which is the lightest atom known and which contains only one electron and one proton, the nuclei of all types of atoms are found to consist of aggregations of both protons and electrons, the protons of course always predominating Helium, the second lightest atom, has a nucleus consisting of a "block" of four protons and two binding electrons, the same as the alpha particle. Then for all other types up to and including uranium, which is the heaviest known atom, these nuclei are composed of increasingly numerous blocks. The more massive the nucleus the greater will be the number of planetary electrons. In other words, whatever number of excess protons there are in the nucleus there will be just that many negative "satellites" revolving around it. Thus the stability of the atom is maintained. The atomic weight of any element is therefore governed by the excess protons in the nucleus. Here then for the first time in the history of chemistry we have a reasonable explanation of why one type of atom differs from another. |
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