Questions? Call Us 1-773-271-0318 9am to 2pm Central Time Mon.-Fri. Q. Is his table the familiar one?
A. No. There were shifts of his 8th column elements into another column, and a column (now called group) of gases added. The current, familiar flat form has been developed with adaptations by Bayley, then Werner, Moseley, and finally, Glenn Seaborg.
Details of answer;
A visual difference between Mendeleev’s layout and that of modern tables, is that in his initial arrangement the element groups were arranged horizontally, so that periods of elements appear in vertical columns instead of the currently common horizontal rows, and more importantly, the elements are now arranged by atomic number rather than by weight, which he, Meyer, and the earlier de Chancourtois employed.
In 1871 Mendeleev revised the 17-group table with eight vertical column groups (The eighth group consisted of what were then considered transition elements). This table exhibited similarities not only in small units such as the triads, but showed similarities in an entire network of vertical, horizontal, and diagonal relationships. The table contained gaps, but Mendeleev predicted the discovery of new elements to fill them.
Lord Rayleigh and William Ramsey greatly enhanced the periodic table by discovering the "inert gases." In 1895 Rayleigh reported the discovery of a new gaseous element named argon, and did not fit any of the known periodic groups. Ramsey followed by discovering the remainder of the inert gases and positioning them in the periodic table. This is the 8th column, now called the noble gases, and the transition elements moved elsewhere. So by 1900, the periodic table was taking a familiar shape with elements arranged by atomic weight.
Soon after Rutherford’s landmark experiment of discovering the nucleus in 1911, Henry Moseley subjected known elements to X-rays. He was able to derive the relationship between X-ray frequency and number of protons. When Moseley arranged the elements according to increasing atomic numbers and not atomic masses, some of the inconsistencies associated with Mendeleev’s table were eliminated. The modern periodic table is based on atomic numbers, and divided into periods, columns, groups, and blocks. There is no universal agreement upon all of these, least of all the blocks, which appears to be strong on dogma and weak on science.
The last widely accepted major change to the periodic table resulted from Glenn Seaborg’s work in the middle of the 20th century, moving the Rare Earths to below the rest of the table. Then, 20 years later, Roy Alexander found a way that was agreeable to Dr. Seaborg to move them back to their correct position by employing Alexander's patented3D form of the table, partcularly useful in layman introduction to the periodic table.
Resources;
wou.edu, ausetute.com.au, mooni.fccj.org, AllPeriodicTables.com
