107 Stories About Chemistry |
There are no elements in Mendeleyev's System which have no place at all. There are elements with no definite place. Such, for instance, is the very first of them, hydrogen. Investigators are still at odds as to whether element No. 1 should be in the first, or in the seventh group of the Periodic Table. Uranium is in much the same predicament. But had not Mendeleyev determined its position once and for all?
For decades no one questioned uranium's being in the sixth group of the Periodic Table as the heaviest member of the family including also chromium, molybdenum and tungsten, and its position seemed quite infallible. But times changed, and uranium was no longer the last in the series of elements. A whole "cohort" of man-made transuranium elements ranged out at its right, and they all had to be placed in the Mendeleyev Table. What groups and what boxes were to be assigned to the transuranium elements? After much controversy a large number of scientists came to the conclusion that they should all be placed together in a single group and in a single box.
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