ELEMENT, in chemistry, a primary sub stance that cannot be decomposed as may be done with compound substances. The different substances now admitted by chem ists to be elements, together with those which are tentatively assumed to be so, until further evidence is accumulated, number (1918) 82. They are aluminum, antimony, argon, arsenic, barium, beryllium, bismuth, boron, bromine, cadmium, cesium, calcium, car bon, cerium, chlorine, chromium, cobalt, copper, dysprosium, erbium, europium, fluorine, gado linium, gallium, germanium, gold, helium, hol mium, hydrogen, indium, iodine iridium, iron, krypton, lanthanum, lead, lithium, lutecium, magnesium, manganese, mercury, molybdenum, neodymium, neon, nicicel, niobium, Tilton, nitro gen, osmium, oxygen, palladium, phosphorus, platinum, potassium, praseodymium, radium, rhodium, rubidium, ruthenium, samarium, scan dium, selenium, silicon, silver, sodium, stron tium, sulphur, tantalum, tellurim, terbium, thallium, thorium, thulium, tin, titanium, tung sten uranium, vanadium, xenon, ytterbium, yttrium, zinc and zirconium. Whether anv of these apparently elementary substances will be proved to be in reality compounds cannot be definitely foretold. The most that can he said is that up to the present time no force has been brought to bear on them sufficient to disrupt the atomic attraction which holds each in its individual form. Much speculation has been indulged in concerning the fundamental struc tural differences that subsist between the atoms of the different elements, but no universally acceptable explanation has yet been offered to account for the fact that the thousands of com pounds that have been studied are all composed of so small a number of essentially different constituents. The alchemists believed that every apparent °element" can be modified, or ((trans muted," into every other one, and much labor was expended in the effort to transmute the baser metals into the ((nobler" or more valu able ones. We now lcnow that the problem of transmutation, if it is capable of solution at all, is at any rate far more serious than it was be lieved to be in the early history of chemistry.
But there are numerous indications which sug gest a relationship among the substances that are now accepted as elements, and it may yet prove to be possible to transform lead into gold, or tin into platinum. For some years past Sir William Crookes has been a consist ent advocate of the theory which teaches that all matter is fundamentally the same, and he has shown that some of the (elements" can be resolved, by fractionation, into substances which exhibit spectra that differ from one another in a marked manner, any two consecutive members of the series showing close similarity in their spectra, while the extreme members of the series are totally dissimilar. (Consult his lecture be fore the Berlin Congress of Applied Chemistry, entitled (Modern Views on Matter,) in Science for 26 June 1903). The theory of matter which is in favor at the present writing teaches that all atoms are composed of electrons (q.v.), 'which are all alike, but which are grouped to gether in various ways, and in various numbers, to form the atoms of the elements. If this view stands the test of further research the possi bility of transmuting the elements into one another may not be altogether fanciful. The element radium (q.v.), which appears to pos sess the singular power of continuously emitting streams of free electrons., occurs in nature in certain varieties of the mineral uraninite. It is notable that the inert gas helium (q.v.) also occurs in this same mineral, though it appears to be present in the free state and never in actual chemical combination. It has been sug gested that we are here face to face with a real case of transmutation of elements, the electrons that are emitted by.the radium being slowly built up, within the uraninite, into new systems, which are nothing less than atoms of helium. See MOLECULAR THEORY; PERIODIC LAW ; RADIATION ; RADIUM.