The periodic table arranges the chemical elements in order of atomic number so that elements with similar properties fall into columns known as groups. The standard periodic table includes periods (horizontal rows) and groups (vertical columns), with elements in the same group having similar properties. Dmitri Mendeleev is credited with developing the first recognizable periodic table in 1869, arranging the known elements based on their atomic masses and properties. While earlier scientists like Lavoisier and Döbereiner identified patterns among elements, Mendeleev's periodic table was the first to systematically organize all known elements and also predict properties of undiscovered elements.

1. The periodic table

2. What is the periodic table ?
• The periodic table is a table of the
chemical elements in which the
elements are arranged by order of
atomic number in such a way that
the periodic properties (chemical
periodicity) of the elements are
made clear.

4. What does the periodic
table include?
The standard form of the table includes
periods (usually horizontal in the periodic
table) and groups (usually vertical).
Elements in groups have some similar
properties to each other. There is no one
single or best structure for the periodic table
but by whatever consensus there is, the
form used here is very useful. The periodic
table is a masterpiece of organised chemical
information.

5. The history of the periodic
table
The history of the periodic table reflects over
a century of growth in the understanding of
chemical properties. The most important
event was the publication of the
first periodic table by Dmitri Mendeleev in
1869.While Mendeleev built upon earlier
discoveries by such scientists as AntoineLaurent de Lavoisier and Stanislao
Cannizzaro, the Russian scientist is
generally given sole credit for development
of the periodic table.

6. Antoine-Laurent de
Lavoisier
Lavoisier's Traité Élémentaire de
Chimie (Elementary Treatise of
Chemistry, 1789, translated into English
by Robert Kerr) is considered to be the
first modern chemical textbook. It
contained a list of elements, or
substances that could not be broken
down further, which
included oxygen, nitrogen, hydrogen, ph
osphorus,mercury, zinc, and sulfur. It also
forms the basis for the modern list of
elements. His list, however, also
included light and caloric, which he
believed to be material substances.

7. Johann Wolfgang
Döbereiner
In 1817, Johann Wolfgang Döbereiner began to
formulate one of the earliest attempts to classify the
elements. In 1828 he found that some elements
formed groups of three with related properties. He
termed these groups "triads". Some triads classified by
Döbereiner are:
chlorine, bromine, and iodine
calcium, strontium, and barium
sulfur, selenium, and tellurium
lithium, sodium, and potassium
In all of the triads, the atomic mass of the second
element was almost exactly the average of the atomic
weights of the first and third elements

8. John Newlands
J. A. R. Newlands' law of
octaves
John Newlands was an
English chemist who in
1865 classified the 56
elements that had been
discovered at the time
into eleven groups which
were based on similar
physical properties.

9. Dmitri Mendeleev
•
Dmitri Mendeleev, a Russian chemist, was
the first scientist to make a periodic
table much like the one we use today.
Mendeleev arranged the elements in a
table ordered by atomic
mass, corresponding to relative molar
mass as defined today. It is sometimes
said that he played "chemical solitaire" on
long train journeys using cards with
various facts of known elements.
• Shortcomings of Mendeleev's table
His table did not include any of the noble
gases, which were discovered later. These
were added by Sir William Ramsay as Group
0, without any disturbance to the basic
concept of the periodic table.
A single position could not be assigned
to hydrogen in the periodic table. Hydrogen
could be placed in the alkali metals group as
well as in the halogens group.

10. How to find group and period
of an element
1. Do the electron configuration
2.
If it ends with s p,it belongs
to the group A.
3. If it ends with s d, it belongs
to the group B.
4. If it ends with f, it belongs to
the B group.
5. The number of group is find
by summing the nr. of
electrons.
6. The period is the biggest
quantum number.

11. Curiosity
Element 117 discovered?
A paper just published (5 April 2010) in Physical Review Letters by Yu. Ts.
Oganessian and others claims the synthesis of a new element with atomic number
117. The abstract states "The discovery of a new chemical element with atomic
number Z=117 is reported. The isotopes 293117 and 294117 were produced in
fusion reactions between 48Ca and 249Bk. Decay chains involving eleven new
nuclei were identified by means of the Dubna Gas Filled Recoil Separator. The
measured decay properties show a strong rise of stability for heavier isotopes with
Z>=111, validating the concept of the long sought island of
enhanced stability for super-heavy nuclei."