PERIODIC TABLE

1
PERIODIC TABLE
2
The periodic table of the chemical elements,
also called the Mendeleev periodic table, is a
tabular display of the known chemical elements.
First created by Dmitri Mendeleev, the elements
were originally arranged by atomic mass. Then in
1911, Henry Moseley rearranged the table more
logically according to atomic number so that many
chemical properties followed a regular pattern
across the table. Each element is listed by its
atomic number and chemical symbol. Mendeleev's
and Moseley's development of the periodic table
was one of the greatest achievements in modern
chemistry. Chemists were able to quantitatively
explain the behavior of the elements, and to
predict the existence of yet undiscovered
ones. There are 116 chemical elements whose
discoveries have been confirmed. Ninety-four can
be found naturally on Earth, and the rest have
been produced in laboratories.
3
HISTORY The original table was created without a
knowledge of the inner structure of atoms if one
orders the elements by atomic mass, and then
plots certain other properties against atomic
mass, one sees an undulation or periodicity to
these properties as a function of atomic mass.
The first to recognize these regularities was the
German chemist Johann Wolfgang Döbereiner who, in
1829, noticed a number of triads of similar
elements
This was followed by the English chemist John
Newlands, who in 1865 noticed that the elements
of similar type recurred at intervals of eight,
which he likened to the octaves of music, though
his law of octaves was ridiculed by his
contemporaries. Finally, in 1869, the German
Julius Lothar Meyer and the Russian chemist
Dmitri Ivanovich Mendeleev almost simultaneously
developed the first periodic table, arranging the
elements by mass. However,
Mendeleev plotted a few elements out of strict
mass sequence in order to make a better match to
the properties of their neighbours in the table,
corrected mistakes in the values of several
atomic masses, and predicted the existence and
properties of a few new elements in the empty
cells of his table. Mendeleev was later
vindicated by the discovery of the electronic
structure of the elements in the late 19th and
early 20th century. In the 1940s Glenn T.
Seaborg identified the transuranic lathanides and
the actinides, which may be placed within the
table, or below (as shown above).
4
Standard
5
Explanation of the structure of the periodic table
The primary determinant of an element's chemical
properties is its electron configuration,
particularly the valence shell electrons. For
instance, all atoms whose four valence electrons
are found on the p shell will behave similarly,
regardless of which energy level that last p
shell is on. The shell in which the atom's
outermost electrons reside determines the "block"
to which it belongs. The number of valence shell
electrons determines which family, or group, the
element belongs.
The total number of electron shells an atom has
determines the period to which it belongs. Each
shell is divided into different subshells, which
as atomic number increases are filled in roughly
this order 1s 2s 2p 3s
3p 4s 3d 4p 5s 4d 5p 6s
5d 6p 7s 6d 7p 4f
5f ...
Dimitri Mendeleev created this, the original,
periodic table
6
Hence the structure of the table. Since the
outermost electrons determine chemical
properties, those with the same number of valence
electrons are grouped together.
Progressing through a group from lightest element
to heaviest element, the outer-shell electrons
(those most readily accessible for participation
in chemical reactions) are all in the same type
of orbital, with a similar shape, but with
increasingly higher energy and average distance
from the nucleus. For instance, the outer-shell
(or "valence") electrons of the first group,
headed by hydrogen all have one electron in an s
orbital. In hydrogen, that s orbital is in the
lowest possible energy state of any atom, the
first-shell orbital (and represented by
hydrogen's position in the first period of the
table). In francium, the heaviest element of the
group, the outer-shell electron is in the
seventh-shell orbital, significantly further out
on average from the nucleus than those electrons
filling all the shells below it in energy. As
another example, both carbon and lead have four
electrons in their outer shell orbitals.
Because of the importance of the outermost shell,
the different regions of the periodic table are
sometimes referred to as periodic table blocks,
named according to the sub-shell in which the
"last" electron resides, e.g. the s-block, the
p-block, the d-block, etc
7
Extended Periodic Table of the Elements
The blue symbol on top of each column shows the
last electron orbital following the Mueller
diagram (note that there are exceptions, like
copper). The red number at the left of each row
shows the period the last electron shell.
Helium is placed next to hydrogen instead of on
top of neon because it is part of the s2 group.
This extended periodic table was suggested by
Glenn T. Seaborg in 1969. It is a logical
extension of the principles behind the standard
periodic table to include as-yet-undiscoved
chemical elements. All of the undiscovered
elements are named by the International Union of
Pure and Applied Chemistry (IUPAC) systematic
element name standard of creating a generic name
until it has been discovered, confirmed and an
official name approved.
8
The alternate table is a periodic table
perpendicularly rotated counterclockwise, hence
like in many writing systems, the lower groups
are to the left and the number increases to the
right.
Due to the rotation and the incorporation of the
lanthanides and actinides into the main table,
the Alternate Table is significant longer
vertically than the Standard Table.
9
Other methods for displaying the chemical elements
Zmaczynski's Periodic Table
10
Benfry's Spiral Periodic Table
11
Stowe table
12
Tarantola's orbital periodic table
13
The Chemical Galaxy is a new periodic table
designed by Philip Stewart in November 2004 based
on the cyclical nature of characteristics of the
chemical elements (which depend principally on
the valence electrons).
In 1951, Edgar Longman showed that arranging the
elements in an elliptical spiral helped reveal
patterns in their properties. This gave the
then-12-year-old Stewart the idea that it
resembled a spiral galaxy. It is designed as an
inspiring supplement to existing periodic tables.
14
THE END
15
Author
16
Bartosz Sobczyk