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Atomic
Structure
The study of nature of matter has been a
perplexing one since the dawn of Modern Science , perhaps in the late
17 th century . Though several views of atoms can be found
in different works in the eastern literatures including Tamil ,
systematic study started only in the western world.
Perhaps Dalton’s Atomic
theory is one such systematic effort, in the late 18th and
early 19th century. Since then several scientists developed
the primitive theory for the better. Some of them are Berzilius who
wrote the first text book of chemistry in 1800;
Avagadro (1800) whose hypothesis has become a law today ;
Cannizero(1850) who developed methods for determining atomic
masses ; Mendeleef (1869),
the father of the periodic table also contributed to the understanding
of atoms.
In the late 18th
century Cathode rays, x-rays and radioactivity were discovered. The Einstein's theory also gave a momentum towards the
understanding of atom. Planks
quantum theory, De-Broglie's quantum mechanics and Heisenberg’s
uncertainity theory , Pauli’s exclusion principle were all evolved
between 1910 and 1920.
With
the discovery high vacuum techniques , conductance of electricity
through gases at low pressure came. This resulted in the
discovery of cathode rays and the sub atomic particle such as electron
and proton.
In 1910 the first nuclear model of atom of Bhor came in to
existence with circular orbits for electron.
Later on it was further expanded to accommodate elliptical
orbitals also in a spherical dimension.
The consequence of quantum theory and quantum mechanics is the
proposal of four quantum numbers.
The filling of electrons in spherical orbitals based on energy,
with the electrons of lower energy occupy at the lower levels and get
filled up in the increasing order of energy came to be known as Aufbau
principle. Thus the
concept of electronic configuration , orbitals came into existence
together with the knowledge of shapes of orbitals. The scope of Atomic
structure is very high , as
it is most important to
understand the basics of chemistry.
Students are advised to gather additional information from
books to satisfy their curiosity and to understand better.
Only
a few important
explanations, illustrations and tables have been included in the
introduction as the scope of this work is highly limited.
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