Техническое чтение для энергетиков. Бухарова Г.П. - 6 стр.

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matter could be converted into energy– very little matter into very great energy –
there was a storm of protest in the scientific world. But little by little the evidence
that he was right accumulated, and within a few years an entirely new picture of the
atom emerged from the studies and laboratories of scientists in many countries. From
that evidence Lord Rutherford, the New Zealand-born scientist, and his young Danish
assistant, Niels Bohr, developed by 1911 their revolutionary theory of what the atom
was really like.
That picture of the atom has since been elaborated and filled in with more
details. It is not yet complete; but its essential features are known to be correct –
otherwise there would be no atomic bombs, which few people would regret, or
nuclear power stations.
Broadly speaking, the atom is a miniature solar system, with a 'sun', the
nucleus, and a number of 'planets', the electrons, revolving around it. All the matter of
the atom is concentrated in the nucleus: there are protons, particles with a positive
electric charge, neutrons, particles without a charge, and some other particles whose
role and nature is still being investigated. The electrons, which have next to no mass
and weight, are negatively charged; in fact, they are the carriers of electricity in all
our electric wires and appliances.
Normally there are as many positive protons in the nucleus as there are
electrons revolving around it, so that their charges cancel each other out and the atom
as a whole is electrically neutral. But if for some reason an atom loses a proton or an
electron or two, its electrical balance is disturbed, it becomes negatively or positively
charged and is called an ion.
The atoms of all the elements contain the same kind of particles; what
distinguishes them from each other is merely the number of particles – of protons in
the nucleus and of electrons revolving around it. Hydrogen, for instance, being the
lightest and simplest element, has only one of each; uranium, the heaviest element
occurring in Nature, has 92. So all you have to do to change one element into another
is either to knock some protons and a corresponding number of electrons off each
atom, or add them; in fact, this process is going on in Nature all the time.
Theoretically, we could change lead into gold, as the alchemists dreamed of doing, by
removing three protons and electrons from a few billion lead atoms, which have 82 of
each, then we would get gold atoms with 79 protons and electron each. However, the
knocking-off process would be much more expensive than the gold we would get.
The neutrons, which are present in the atoms of many elements, are of
particular importance in the utilization of atomic energy. Most elements are mixtures
of ordinary atoms and so-called isotopes: the isotope atoms have more, or fewer,
neutrons than the ordinary atoms. An isotope differs from the ordinary form of the
element only in weight, but chemically it behaves in exactly the same way. Water, for
instance, is a mixture of ordinary molecules of hydrogen and oxygen atoms and of
'heavy' ones. The heavy hydrogen atom has an extra neutron in its nucleus.
Uranium, on the other hand, has an jsotope whose nucleus contains fewer neutrons
than the ordinary element. This isotope – atomic weight: 235; atomic weight of
ordinary uranium: 238 – has a very special significance in nuclear physics because it

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