The PERIODIC TABLE of the chemical elements is an incredibly useful icon of chemistry, arrived at by a series of developments and observations by experimental scientists, crystallizing in the mid-1800s.

Developed by awareness of repetitions in the property similarities of the known elements, it was charted by Dmitri Mendeleyev for his students (see at right) , and first published in 1869 with his "periodic law" presenting that the sequence of elements depended on their weights (later changed to atomic number sequence).

The "fearful symmetry" was evolved, as he said, "independently of any conception as to the nature of the elements." Recent knowledge gained of the structure of atoms has gone far towards explaining the shape of the periodic table, and songs of praise have been sung to it's beauty and power.

The table has undergone many changes; addition of elements, more accurate values, modified references, different column labels, and shifts in element positions.

A quick loading, recently updated version of the flat periodic table, useful for reference, can be seen by clicking here, and it leads to one you can print out.

A number of problems with equating the periodic table with the periodic law have been resolved by the recognition that relationships between elements are more clearly and accurately shown in three-dimensional representations.