The
Modern
Periodic
Unit One Chemistry – Horsham College
Table
Chapter 4 – VCE Chemistry
Periodic Table Development
• No chemistry textbook, classroom, lecture
theatre or research laboratory is complete
without a copy of the periodic table of the
elements.
• Chemists attempted 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 realised 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.
• Today there are 111 elements recognised
by IUPAC, and these are usually displayed
in the form of a matrix called a periodic
table.
What Patterns?
• Before the 1800’s, scientists and
alchemists did not consider the
idea of patterns occurring
between the known elements.
• Elements were considered unique
and unrelated to any other
element.
• Scientists who suggested that
patterns may exist were ridiculed.
• Sodium and Potassium were
discovered in the early 1800’s.
Both have very similar properties.
• Empirical evidence later
suggested that elements could be
sorted in order of increasing
atomic weight
• Elements were found to
have repeating patterns.
This is known as the
periodic law.
• The advancing knowledge
of the atomic model
furthered chemists
knowledge of elemental
properties.
Early classification Antoine Lavoisier of 1789
• Antoine Lavoisier's 1789 classification of substances divided
substances into four 'element' groups.
• The list contained substances that could not be broken down
further.
1. Acid-making elements; Sulphur, Phosphorus, charcoal
2. gas-like elements; Light, caloric (heat), oxygen
3. metallic elements; cobalt, mercury, tin, copper, nickel, iron, gold,
lead, silver, zinc, manganese, tungsten, platinum
4. earthy elements; lime, magnesia, barytes, azote, argilla, silex
Lavoisier also formed the basis for the modern list of elements.
Döbereiner’s Triads
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In 1829, German Johann Döbereiner
discovered that groups of elements
with similar chemical properties such
as Lithium, Sodium and Potassium
had a strange similarity.
The average of the atomic weight of
Lithium and Potassium was the same
as the atomic weight of Sodium.
The middle element in the triad had
properties halfway between the
properties of the other two.
This pattern was replicated with
Calcium, Strontium and Barium as
well as Sulphur, Selenium, and
Tellurium and also Chlorine, Bromine
and Iodine.
In addition, the densities of some of
the triads followed the same
relationship.
These groups became known as
"Döbereiner's triads".
Ca Sr Ba
40 88 137
(40 + 137) ÷ 2 = 88
The Cylinder of
Elements
• In 1862, Frenchman
Alexandre de
Chancourtois published a
cylindrical arrangement of
the elements (Also called
the telluric screw).
• The elements, based on
Oxygen-16, differed by
16 in their atomic weight.
• Like Döbereiner,
Chancourtois’ cylinder
received little attention.
The Law of Octaves
• English Chemist, John Newlands
discovered that every eighth
element had similar properties.
• He called this the law of octaves
(Analogy with music).
• Newlands developed a table in
which he placed elements with
similar properties in the same
collum.
• Unfortunately, his table was
ridiculed by the Royal Society in
1864.
However, while successful for
some elements, Newlands'
law of octaves failed for two
reasons:
1. It was not valid for elements
that had atomic masses
higher than Ca.
2. When further elements were
discovered, such as the
noble gases (He, Ne, Ar),
they could not be
accommodated in his table.
John Newlands
Questions 4.1
• Complete questions 1-4 on P. 72 of
Nelson VCE Chemistry.
Mendeleev and Meyer
• Russian Dmitri Mendeleev
and German Julius von
Meyer went on to
independently develop their
versions of the periodic law.
• Both chemists produced
remarkably similar results at
the same time working
independently of one
another.
• Therefore, there has been
some disagreement about
who deserves credit for
being the "father" of the
periodic table
Dmitri Mendeleev
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In 1869 Mendeleev arranged elements
by atomic weights and properties.
Mendeleev's periodic table of 1869
contained 17 columns with two partial
periods of seven elements each (Li-F
& Na-Cl) followed by two nearly
complete periods (K-Br & Rb-I).
In 1871 Mendeleev revised the 17group table with eight columns (the
eighth group consisted of 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.
In 1906, Mendeleev came within one
vote of receiving the Nobel Prize in
chemistry.
Julius von Meyer
• Julius von Meyer also developed
a periodic table based on atomic
masses, independently of
Mendeleev.
• However, Meyer presented only
28 elements.
• Meyer had several inaccuracies
and some elements were not
included.
• Meyer was the first scientist to
introduce the concept of valence
as a periodic property.
• Also, Meyer never came to the
idea of predicting new elements
and correcting atomic weights.
• Only a few months after
Mendeleev published his
periodic table of all known
elements (and predicted
several new elements to
complete the table, plus
some corrected atomic
weights), Meyer published
a virtually identical table.
Questions 4.2
• Complete questions 1-5 on P. 75 of
Nelson VCE Chemistry.
Henry Moseley
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Using atomic number instead of
atomic mass as the organising
principle was first proposed by the
British chemist Henry Moseley in
1913.
Before this discovery, atomic numbers
were just sequential numbers based
on an element's atomic weight.
Moseley's discovery showed that
atomic numbers had an
experimentally measurable basis.
Atomic number solved anomalies like
Iodine, that has a higher atomic
number than tellurium - so, even
though he didn't know why,
Mendeleev was right to place it after
tellurium after all!
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Moseley's research also
showed that there were gaps
in his table at atomic
numbers 43 and 61 which
are now known to be
radioactive and not naturally
occurring.
Following in the footsteps of
Dmitri Mendeleyev, Henry
Moseley also predicted new
elements.
Glenn Seaborg
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In the 1930s, the heaviest elements were
being put up in the body of the periodic table
Glenn Seaborg "plucked those out" while
working with Fermi in Chicago, naming them
the Actinide series.
This later permitted proper placement of
subsequently 'created' elements - the
Transactinides, changing the periodic table
yet again.
These elements were shown separate from
the main body of the table.
The concept demonstrated how the heavy
elements fit into the Periodic Table and thus
demonstrated their relationships to the other
elements.
In addition to the discovery of transuranium
elements, Seaborg and his colleagues are
responsible for the identification of more than
100 isotopes of elements throughout the
Periodic Table.
The Periods of the Periodic
Table
• The horizontal rows of
the table are called
periods.
• There are 7 periods.
• Elements in the same
period have the same
outermost occupied
shell.
Example – Period 2 is
filling the second shell.
The Groups of the Periodic
Table
• The vertical columns are called groups.
• Groups are numbered 1-18. This replaces the old
system of I-VIII.
• Groups families have the same number of valence
electrons in their valence (outermost) shell.
The periodic table groups are as follows (in the brackets are shown the old
systems: European and American):
• Group 1 (IA,IA): the alkali metals or hydrogen family/lithium family
• Group 2 (IIA,IIA): the alkaline earth metals or helium family/beryllium
family
• Group 3 (IIIA,IIIB): the scandium family
• Group 4 (IVA,IVB): the titanium family
• Group 5 (VA,VB): the vanadium family
• Group 6 (VIA,VIB): the chromium family
• Group 7 (VIIA,VIIB): the manganese family
• Group 8 (VIII): the iron family
• Group 9 (VIII): the cobalt family
• Group 10 (VIII): the nickel family
• Group 11 (IB,IB): the coinage metals (not an IUPAC-recommended name)
or copper family
• Group 12 (IIB,IIB): the zinc family
• Group 13 (IIIB,IIIA): the boron family
• Group 14 (IVB,IVA): the carbon family
• Group 15 (VB,VA): the pnictogens (not an IUPAC-recommended name) or
nitrogen family
• Group 16 (VIB,VIA): the chalcogens or oxygen family
• Group 17 (VIIB,VIIA): the halogens or fluorine family
• Group 18 (Group 0): the noble gases or helium family/neon family
Questions 4.3
• Complete questions 1-5 on P. 80 of
Nelson VCE Chemistry.
The Blocks of the Periodic
Table (s-block)
The s-block
• The s subshell of the valence shell is
being filled.
• Since a s subshell holds 2 electrons,
only 2 groups of elements (Groups 1
& 2) are in this block
Facts
• In the outermost occupied shell there
are 1 or 2 electrons in the s subshell
but none in the p subshell.
• If the second outermost shell
contains a d subshell, it does not
contain electrons.
The Blocks of the Periodic
Table (p-block)
The p-block
• The p subshell of the outermost
shell is being filled.
• A p subshell can hold only 6
electrons, hence there are 6
groups in the p-block
Facts
• In the outermost occupied shell
there are 2 electrons in the s
subshell and 1 or more
electrons in the p subshell.
• If the second outermost shell
contains a d subshell, it is full.
The Blocks of the Periodic
Table (d-block)
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The d subshell is being filled.
Due to the order of of energies of the subshells, this only occurs after the next shell
has started to fill.
• A d subshell can hold 10 electrons, hence 10 groups are found in the d-block.
• Metals in this block are collectively known as the transition metals.
• 3d subshell filling elements are called first transition series. 4d are second etc.
Electron configuration;
• In the outermost occupied shell the s subshell is full but there are no electons in the
p subshell.
• The d subshell of the second outermost shell contain 1 or more electrons
Questions 4.4
• Complete questions 1-5 on P. 83
of Nelson VCE Chemistry.
The Noble Gases
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The noble gases are found in group 18 of the modern periodic table. They were not
included in the original periodic table.
Noble gases are found in minerals or in the atmosphere in trace amounts.
Noble gases are un-reactive (inert) due to having a full outer shell.
Henry Cavendish, in 1784, placed some air and pure oxygen into a U-shaped tube that
contained mercury.
He then added some salts and a base to the mercury. Cavendish used a electric
discharge to start the reaction.
These reactions removed the nitrogen and oxygen from the air.
Surprisingly a bubble remained in the top of the tube.
This unreactive bubble was called ‘Cavendish’s bubble’.
More than 100 years, this bubble was named Argon meaning Greek for ‘lazy one’.
Rayleigh and Ramsey
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In the late nineteenth century, Lord
Rayleigh and William Ramsay
theorised that the nitrogen extracted
from air was associated with another
gas, argon.
With this discovery, they realized that
a whole class of gases was missing
from the periodic table.
Eventually all the known noble gases
except for helium were discovered in
the air, with argon being much more
common than the others, and the
table was completed.
Helium was detected
spectrographically in the Sun in 1868.
The isolation of helium on Earth had
to wait until 1895.
Radon was isolated and studied in
1910 after many years of investigating
by Ramsey. Radon is radioactive.
Elements known before 1700:
Elements known before 1700, plus those discovered
between 1700 and 1799:
Elements known before 1800, plus those discovered
between 1800 and 1899:
Elements known before 1900, plus those discovered
between 1900 and 2005:
The Missing Elements
• By 1925, 88 out of the 92 naturally occurring elements had been
identified.
• Elements 43 (Technetium) ,61 (Promethium), 85 (Astatine) and 87
(Francium) were missing.
• All are radioactive with very short half-lives.
• 61,85 and 87 have been identified in decaying uranium. All are
extremely rare.
• 43 has only been produced synthetically.
• The periodic table is now complete!
Alternative Tables
The periodic spiral of Professor Thoedor
Benfey.
Alternative Tables
Albert Tarantola’s orbital periodic table.
Alternative Tables
Alexander Arrangement of the Elements
Stowe’s Arrangement
Questions 4.5
• Complete questions 1-4 on P. 86
of Nelson VCE Chemistry.
Review Questions
• Complete questions 1-8 on P. 8889 of Nelson VCE Chemistry.