lunes, 11 de octubre de 2010

Evolution and history of atomic model in the century

Each substance in the universe is composed of tiny particles called atoms.
These small particles are studied in chemistry, science grew into middle age and studying the subject.
To understand these atoms along different scientists in history have articulated a number of theories that help us understand the complexity of these particles. These theories mean the settlement of modern chemistry.



450 BCE - Democritus Atomic Model.The development philosophy of Democritus postulated the impossibility of infinite division of matter and the consequent need for the existence of a minimum unit, which would be composed of all substances.





In the fourth century C., Empedocles postulated that matter was composed of 4 elements: earth, air, water and fire.
1803 - John Dalton Atomic Model
John Dalton in 1803 presented his atomic model weights based on the laws, retained the term atom for small particles that form matter. The basic statements of the model are: The matter consists of tiny particles called atoms. The atoms of the same element are equal to each other, especially in weight. The atoms of one element different, are different

After Dalton statement is theory, triggered a series of events that were making changes to the initial atomic model.


 1897 - Joseph Thomson Atomic Model
Thomson assumed that the electrons are distributed in a uniform manner around the atom, known as model raisin cake, can be defined as a static structure.


1911 - Ernest Rutherford Atomic Model
He proved that atoms were not solid, as previously believed, but are mostly empty and its center is a tiny core. Deduced that the atom should be formed by a crust with electrons orbiting a positively charged nucleus


1916 - Arnold Sommerfeld Atomic Model
Is the correction and supplementation of Bohr atom, but not able to demonstrate emission forms elliptical orbits, just ditched its circular shape




1922 - Niels Bohr Atomic Model
Postulated that the electron spin at high speeds around the atomic nucleus. In that case, the electrons are arranged in various circular orbits, which determine different levels of energy.


1926 - Erwin Schrödinger Atomic Theory
In this model the electron originally envisaged as a matter wave whose amplitude decayed rapidly to exceed the atomic radius.

1932 - James Chadwick Atomic Theory
 Discovered a third type of subatomic particles which he called the neutron

1917 - Gilbert Lewis Atomic Theory
Atoms can obtain stable electron configuration by sharing electrons, atom obtained noble gas stable configuration when its last layer has 8 electrons