The periodic
Table of the
Elements
by
Andrei Nesterovitch,
Biology Department,
Stephen F. Austin State University.
BTC 575
Instructor – Dr. A. Van Kley
Introduction
No chemistry textbook, classroom, lecture theatre or
research laboratory is complete without a copy of the
periodic table of the elements. Since the earliest days of
chemistry, attempts have been made to arrange the
known elements in ways that revealed similarities
between them. However, it required the genius of
Mendeleev to see that arranging elements into patterns
was not enough; he realized that there was a natural plan
in which each element has its allotted place, and this
applies not only to the known elements but to some that
were still undiscovered.
Introduction
Mendeleev’s periodic table of 1869 seems all the more
remarkable when we consider his relative isolation from
the main centres of chemical research in Western
Europe, and the rather naive attempts made by scientists
in those centres to bring some sort of order to the growing
list of chemical elements.
Introduction
Because atomic weight, relative atomic mass, is roughly
proportional to atomic number, and because valency, which
manifests itself in the chemical composition, is based on the
outermost electrons of an atom, Mendeleev had chosen the
two properties that in his day most nearly reflected the
fundamental principles on which the table today is based.
Consciously or subconsciously, he arrived at the idea that a
table existed with positions that were to be occupied by the
elements, rather than the other way round - that the known
elements determined the arrangement of the table, as others
imagined.
History
By the end of the 1700s only about 30 elements had
been identified. These elements were mostly metals
such as copper, silver and gold that had been known
and used for currency and jewelry since prehistoric
times.
By the early 1800 scientists were using new laboratory
technique to discover new elements. In less than 100
years scientists doubled the number of known elements.
History
Döbereiner, Johann (1780-1849)
In the early 1817 Johann Dobereiner found that barium,
calcium and strontium had very similar properties. He
put these elements together in groups called a triad. He
also put the elements in order according to their
masses. He found that the middle elements in each
group had a mass that is about half way between the
other two. Dobereiner found several groups of three that
worked together in the same way. This was the
beginning of looking for trend in the arrangements of
elements.
History
Döbereiner, Johann (1780-1849)
Such triads as lithium, sodium and potassium, sulfur,
selenium and tellurium or chlorine, bromine and iodine are
clear examples. By 1843 when Leopold Gmelin published
the first edition of his famous Handbook der Chemie , three
tetrads and even a pentad - nitrogen, phosphorus, arsenic,
antimony and bismuth - which we now recognize as group
15 of the p-block of the periodic table.
History
Stanislao Cannizzaro (1826–1910)
No real progress was going to be made in classifying
elements until the one essential property common to them
all, their atomic weight, was settled. This was done by
Stanislao Cannizzaro (fellow of Amadeo Avogadro) in 1858.
Prior to this, equivalent weights were used and for many
elements there were several equivalent weights, depending
upon the elements oxidation state.
History
Béguyer de Chancourtois (1820–1886)
Béguyer de Chancourtois (French geologist) in 1862 was
the first person to make use of atomic weights to reveal
periodicity. He drew the elements as a continuous spiral
around a cylinder divided into 16 parts. The atomic weight
of oxygen was taken as 16 and used as the standard
against which all others were compared. Chancourtois
noticed that certain of the triads appeared below one
another in his spiral. In particular the tetrad oxygen,
sulfur, selenium and tellurium fell together, and he called
his device the “telluric screw”.
History
Béguyer de Chancourtois (1820–1886)
The atomic weights of these elements are 16,32,79 and
128, respectively, and quite fortuitously they are multiples or
near multiples, of 16. Other parts of the screw were less
successful. Thus boron and aluminium come together all
right but are then followed by nickel, arsenic, lanthanum and
palladium. Chancourtois had discovered periodicity, but had
got the frequency wrong.
History
Newlands, John (1837-1898)
In 1863, almost 50 years after Doberiner developed his triad
John Newlends (Professor of Chemistry at the School of
Medicine for Women, London) developed a new method for
organizing elements. In those 50 years science has
progressed and more elements were known. Newlands took
Doberieners basic ideas and expanded on them. He
organized his elements by mass and property too, but he
added a twist. Dobereiner had work only in small groups, but
Newlands wanted to relate all the elements to each other. He
discovered a repetition in the properties of elements.
History
Newlands, John (1837-1898)
He chose a table of seven columns and entered his
elements in increasing order of atomic weight. This
arrangement produced some misalignments, but
Newlands was sufficiently secure in his chemical
knowledge to put similar elements in the same column
even if it meant squashing two elements into some of his
boxes.
History
Newlands, John (1837-1898)
By analogy with the tonic scale of seven musical notes and
their octaves, Newlands called his discovery of periodicity
the ‘Law of Octaves’. His efforts were criticized, indeed
were publicly ridiculed, by members of the chemical
fraternity and it was only in 1887, 18 years after
Mendeleev’s work that Newlands’s contribution was
recognised by the Royal Society, which awarded him the
Davy Metal.
History
Julius Lothar Meyer (1830–1895)
The German chemist Julius Lothar Meyer also used
Cannizzaro’s atomic weights to draw up a primitive table in
1864, but the more sophisticated version he produced in
1868 for the second edition of his textbook was not used
and remained among his papers to be published only after
his death in 1895. However, what Meyer did was to publish
in 1870 a graph which plotted atomic volumes against
atomic weights.
History
Julius Lothar Meyer (1830–1895)
History
Julius Lothar Meyer (1830–1895)
This clearly showed the periodic changes of this property,
with maximum atomic volumes at intervals of 7, 7, 14 and
15. With the inclusion of undiscovered elements this
graph would have revealed the observed intervals of 8, 8,
18 and 18 of the first four rows of the modern table.
History
Julius Lothar Meyer (1830–1895)
Meyer published too late to claim priority over Mendeleev but
just in time to confirm that the latter’s discovery of the periodic
table was based on sound chemical principles. Although
Mendeleev published his tables in the new and obscure
journal of the Russian Chemical Society, his paper was
abstracted within weeks of its appearance into the German
journal Zeitschrift für Chemie, and well before Meyer’s paper
was published in December of that year, 1869.
Mendeleev’s discovery
The fateful day for Mendeleev was 17 February 1869 (Julian
calendar). He cancelled a planned visit to a factory and stayed
at home working on the problem of how to arrange the
chemical elements in a systematic way. To aid him in this
endeavor he wrote each element and its chief properties on a
separate card and began to lay these out in various patterns.
Mendeleev’s discovery
Eventually he achieved a layout that suited him and
copied it down on paper. Later that same day he
decided a better arrangement was possible and made a
copy of that, which had similar elements grouped in
vertical columns, unlike his first table, which grouped
them horizontally. These historic documents still exist.
That Mendeleev realized that he had discovered, rather
than designed, the periodic table is shown by his
attitude towards it.
Mendeleev’s discovery
Mendeleev’s discovery
First, he left gaps in it for missing elements. Leaving such
gaps in tables of elements was not in itself new, but
Mendeleev was so sure of himself that he was prepared to
predict the physical and chemical properties of these
undiscovered elements. His most notable successes were
with eka aluminium (= Gallium) and eka-silicon (=
germanium). Lecoq de Boisbaudran discovered gallium in
1875 and reported its density as 4.7g cm -3, which did not
agree with Mendeleev’s prediction of 5.9 g cm -3.
Mendeleev’s discovery
When he was told that his new element was Mendeleev’s
eka-aluminium, and had most of its properties foretold
accurately, Boisbaudran redetermined its density more
accurately and found it to be as predicted, 5.956 g cm -3.
There could be no doubt now that Mendeleev had discovered
a fundamental pattern of Nature.
Mendeleev’s discovery
Modern Table
The biography of
D. Mendeleev
The biography of
D. Mendeleev
The biography of
D. Mendeleev
Born in Tobolsk (Siberia) he was youngest of 14
children. His father was the Principal of a
gymnasium. Mother was the exceptional member
of the faimily: A brilliant and beautiful woman self
educated by studying all of her brother's stuff (who
did attend university) - very prominent siberian
family published the first newspaper in Siberia. In
1848 his father died, and Mendeleev and mother
walk 1000 miles to Moscow to get Dimitry into the
University.
The biography of
D. Mendeleev
He was not admitted and he and his mother then
walked to St Petersburg where he did get into the
institute of Pedagogy in 1860. In 1869 he received a
government grant to go and get his Ph.D in Paris
with the Physicist Renault.
He became Professor of General Chemistry at the
University of Petrograd (St. Petersburg) in 1866.
The biography of
D. Mendeleev
In 1893 he was asked to head up the Bureau of
Weights and Measures. Accepted and did a
marvelous job.
Died in 1907 of influenza. Published over 262
papers on virtually everything and many huge books
and treatises.
Coin to memorize D. I. Mendeleev
(150-year Anniversary)