The Periodic Table and Transuranium Elements
The periodic table of elements represents a collaborative effort that crosses centuries and continents.
Many researchers contributed to solving this atomic puzzle. In so doing, they designed an adaptable tool
that has accommodated a growing understanding of chemistry and the discovery of new elements.
A pattern emerges
In the late 1860s, University of
Saint Petersburg chemistry
professor Dmitri Mendeleev was
working on a second volume of
his 1861 textbook, “Principles of
Chemistry.” Looking for a simple
way to classify elements “by
some exact, definite principle,”
he drew up a table. A pattern
emerged: an obvious periodicity
of chemical behaviors as a
function of atomic mass. In
March of 1869, Mendeleev
delivered his discovery in a
roughly drawn sketch to the
Russian Chemical Society and
published it later that year.
Two contemporary chemists —
Karlsruhe professor Lothar
Meyer (Germany) and industrial
chemist John Newlands
(England) — envisioned and
published similar charts around
the same time.
Since then, the table’s form has
evolved as researchers filled in
gaps in knowledge and worked
through serious disagreements
on what should be placed where,
and why. The table organized
elements into columns based on
their atomic number, electron
configuration and chemical
properties. This allowed
researchers to predict the
properties and behavior of as-yet
undiscovered elements.
Several prominent U.S. chemists
made vital contributions. At
Harvard University, Theodore W.
Richards and his graduate
students remeasured the atomic
weight of over 30 elements to
pinpoint accuracy. Later, during
Richard’s investigation of lead,
he found that its atomic mass
depended on the metal’s source.
The discovery validated British
chemist Frederick Soddy’s theory
of isotopes and provided nuance
and depth to the ever-more-
robust periodic table.
Richards and others provided
sophisticated atomic mass
measurements to U.S.
Geological Survey Chief Chemist
Frank W. Clarke, who in 1872
had been tasked to compile and
produce an annual table of
elemental weights. Clarke also
chaired the International
Committee on Atomic Weights,
which published the table for an
international audience, revising it
annually until the work stalled in
1918 because of the ongoing
First World War.
While Clarke and others were
compiling data, Francis Preston
Venable, a chemistry professor
at the University of North
Carolina, wondered why the
periodic table was not used
more, especially by teachers. He
came to the conclusion that
Mendeleev’s table and those
created by others were not
terribly inspiring.
Periodic law
In 1896, Venable published the
first history of the periodic law.
With his students in mind, he
redrew the periodic table without
the transition “periods” to simplify
the graphic representation. (A
period is a row within the table.)
Confident in his ability to get
complex topics across to
students, in 1898 Venable co-
wrote a chemistry textbook with
James Lewis Howe, “Inorganic
Chemistry According to the
Periodic Law.”