the periodic table
DESCRIPTION
the periodic table/the history of the periodic table.TRANSCRIPT
The periodic table
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.
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.
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 Antoine-Laurent de
Lavoisier and Stanislao Cannizzaro, the Russian scientist is generally given sole credit
for development of the periodic table.
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, phosphorus,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.
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 iodinecalcium, strontium, and bariumsulfur, selenium, and telluriumlithium, 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
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.
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 tableHis 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.
How to find group and period of an element
1. Do the electron configuration2. 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.
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."