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PROTOPLASM 



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would eventually run down, and then, too, why this tremendous 

 waste of energy? But one of the postulates of the Bohr theory 

 is that no energy is spent (except during radiative transitions). 

 The dynamic atom was preferred by physicists and is now gen- 

 erally accepted. 



According to the theory of Bohr, as amplified by modern 

 concepts, hydrogen, the lightest and simplest element, contains 

 ^— ^ a central nucleus consisting of a proton, which is 

 one elemental particle, or neutron, plus one positive 

 electrical charge, or positron (Fig. 169). Outside 

 this, revolving in an orbit, is a planet of one 

 negative charge — the negative electron, or negatron 

 (the negative electron is presumably the larger of 

 the two, but the proton is much the heavier, being 

 nearly two thousand times the weight of the 

 former). Thus is the essential mass of the atom centered in 

 the nucleus. The distance between the "sun" and "planet" is 

 very great in proportion to their sizes, just as in our solar 

 system, which leads to the startling conclusion that the atom, 

 and consequently all matter, is mostly space. 



To account for certain energy relationships, Bohr carried his 

 concept of atomic structure still further. He assumed that the 



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Fig. 169.— 

 Diagram of 

 the hydrogen 

 atom. 



Fig. 170.— Diagram of the various possible orbits, K, L, M, N, of the hydrogen 



atom. 



lone negative electron of hydrogen has an inner orbit where it 

 normally revolves but that it may travel in several other outer 

 orbits to which it jumps and stays a while, though its natural 

 tendency is to migrate back to the innermost orbit (Fig. 170). 

 The several orbits or energy levels in which the electron may 

 travel have been lettered K, L, M, etc. Owing to an attraction 

 between the planetary electron and the nucleus (due to elec- 



