The Periodic Table
Mendeleyev. Born in 1834. Rose to prominence in 1869.
Known for his wild hair and beard which he had trimmed just once a
year In 1869, he began to toy with a way to arrange the elements.
At the time, elements were normally grouped in one of two ways,
by atomic weight or by common properties. Mendeleyev’s
breakthrough was to see that the two could be combined in a single
table. Mendeleyev place the elements into groups of seven when
they appeared to repeat certain properties. Because the
properties repeated themselves periodically, the invention became known
as the periodic table.
He arranged elements in horizontal rows called periods and vertical
columns called groups (or families). The instantly showed one set
of relationships when read up and down, and another when read from side
to side. The vertical columns put together chemicals that have
similar properties. The horizontal rows arrange the chemicals in
ascending order by the number of protons in their nuclei--what is known
as their atomic number.
Today we have “120 or so” known elements--ninety two
naturally occurring ones plus a couple of dozen that have been created
in labs. In Mendeleyev’s day just sixty-three elements were
known, but part of his cleverness was to realize that the elements then
known didn’t make a complete picture, that many pieces were
missing. His table predicted, very accurately, where new elements would
fit in when they were found. No one knows how high the number of
elements might go, but what is certain is that anything that IS found
will fit neatly into Mendeleyev’s great scheme.