The periodic Table of the Elements

1
The periodic Table of the Elements

• by
• Andrei Nesterovitch,
• Biology Department,
• Stephen F. Austin State University.

BTC 575 Instructor Dr. A. Van Kley
2
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.
3
Introduction
Mendeleevs 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.
4
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.
5
History
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.
6
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.
7
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.
8
History
Stanislao Cannizzaro (18261910)
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.
9
History
Béguyer de Chancourtois (18201886)
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.
10
History
Béguyer de Chancourtois (18201886)
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.
11
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.
12
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.
13
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
Mendeleevs work that Newlandss contribution was
recognised by the Royal Society, which awarded
him the Davy Metal.
14
History
Julius Lothar Meyer (18301895)
The German chemist Julius Lothar Meyer also used
Cannizzaros 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.
15
History
Julius Lothar Meyer (18301895)
16
History
Julius Lothar Meyer (18301895)
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.
17
History
Julius Lothar Meyer (18301895)
Meyer published too late to claim priority over
Mendeleev but just in time to confirm that the
latters 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 Meyers paper was
published in December of that year, 1869.
18
Mendeleevs 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.
19
Mendeleevs 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.
20
Mendeleevs discovery
21
Mendeleevs 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
Mendeleevs prediction of 5.9 g cm -3.
22
Mendeleevs discovery
When he was told that his new element was
Mendeleevs 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.
23
Mendeleevs discovery
24
Modern Table
25
The biography of D. Mendeleev
26
The biography of D. Mendeleev
27
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.
28
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.
29
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.
30
Coin to memorize D. I. Mendeleev (150-year
Anniversary)