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Historical Development Of Atomic Models

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can sinman

on 27 December 2015

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Transcript of Historical Development Of Atomic Models

Historical Development Of Atomic Models
1 November 400
31 October 460
30 October 1803
John Dalton
Michael Faraday
Sir William Crooks
William Conrad Roentgen
J.J Thomson
28 October 1897
His theory was based on the four elements.These elements are fire,air,earth and water.
He found the first the atomic model.
He did his experiment by 5 human senses.He believed that all of the particles are made up from a small particle called atom.His model was not accepted because Aristotle was more famous than Democritus in Greek Era.
His experiment was observing the chemical reactions.By looking at how things reacted and recombined to form new substances, Dalton was able to build on Democritus' idea of atoms as the fundamental building block's of matter and go further to say that there were many different "flavors" or kinds of atoms.
His models were billiard balls for atoms.
Theories of Dalton:
All matters are made up from small particles called atoms.
Atoms are indivisible.
Atoms can not be created or destroyed.
Atoms are combine with each other in small,definite and integral ratios to form compounds.
Atoms of one element can not be converted to atoms of another element.
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism.
He developed the cathode rays.It was a vacuum pump.
His conclusion is cathode rays are negatively charged by studying deflection
of cathode rays by magnetic fields.
28 October1895
He was the person that discovered the
electromagnetic radiation in a wavelentgh
.We called these as
today.He won nobel prize by this experiment.
Thomson discovered the electron in the year 1897. He created a new theory, that atom was made up of
small particles
. He proved his theory using the cathode ray tube.
They passed an electric current through a vacuum tube. They saw a light glowing inside the tube. It travelled in a straight line. They could not explain the phenomenon. Thomson did more experiments on the cathode tube. He placed two electric plates on its path. One was positively charged. The other was negatively charged. The glowing light bent towards the positively charged plate.and found that the glowing materials bent towards the positively charged plate. He found out that the glowing light were smaller particles. They were smaller than the atom. Thus Thomson found the particle called electron. Thus J.J.Thomson's atomic theory was found.
We can understant that atom is the smallest molecule in our body.

He was born in New Zealand. He's physicist who became known as the father of nuclear physics. He discovered the atomic nucleus and explained Peach Pit Model.
His experiment;
An atom is mostly empty space because particles pass through the foil.A particle bounced backwards after striking the dense nucleus.

Max Plank
Max Plank is the German physicist that found the quantum theory of the energy. His work contributed significantly to the understanding of
atomic and subatomic processes
He showed (from purely formal / mathematical foundations) that light must be emitted and absorbed in discrete amounts if it was to correctly describe observed phenomena.
Henry Moseley
Henry Moseley was a English-physicst and he discovered the empirical and chemical concept of the atomic number through Moseley's law in X-ray spectra. Also he determined that when the
proton number

is changed the properties of nucleus is also changed.
Niels Bohr
Niels Bohr was born in Danimark. He's physicist who made foundational contributions to understanding
atomic structure
quantum theory
. He applies quantum theory to
Rutherford's atomic structure
by assuming that electrons travel in stationary orbits defined by their angular momentum. This led to the calculation of possible energy levels for these orbits and the postulation that the emission of light occurs when an electron moves into a lower energy orbit.
Today still we use Bohr's atomic model.

His atomic theory is based on hydrogen atoms.
Electrons of hydrogen atoms are travels in circular orbits and orbits are quantized.When the electons of hydrogen atoms gain energy by absorbing light,they go tot the higher energy level but when they lose energy they emitted the form of quantum of life.
Quantum Theory and Liquid Droplet Theory
Electron can be viewed in two ways, either as a particle or as a wave, but never both at the same time.

This concept, which forms the basis of early quantum theory, also explains that regardless of how one views an electron, all understanding of its properties must be rooted in empirical measurement. Bohr's theory stresses the point that an experiment's results are deeply affected by the measurement tools used to carry them out.

Bohr's theoretical work contributed significantly to scientists' understanding of nuclear fission. According to his liquid droplet theory, a liquid drop provides an accurate representation of an atom's nucleus.

This theory was instrumental in the first attempts to split uranium atoms in the 1930s, an important step in the development of the atomic bomb.

Heisenberg was a German theoretical physicist and one of the key creators of quantum mechanics.His atomic theory was based on uncertainty principle.For uncertainty principle we can not know the place of the electron because we do not their position and velocity.
His experiment was based on a lamp and flies.He thought that the lamp as a nucleus and flies as the electrons.
Thomas Young
Thomas Young performed his famous double slit experiment which seemed to prove that light was a wave. This experiment had profound implications, determining most of nineteenth century physics and resulting in several attempts to discover the ether, or the medium of light propagation. Though the experiment is most notable with light, the fact is that this sort of experiment can be performed with any type of wave, such as water.
Double Split Experiment
Amadeo Avogadro
Amadeo Avogadro (1776-1856) proposed what is now known as Avogadro's Hypothesis in 1811. The hypothesis states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms. When this is combined with Gay-Lussac's Law of Combining Volumes, the only possible formulas for hydrogen, oxygen and water are H2, O2 and H2O, respectively. The solution to the atomic weight problem was at hand in 1811. However, Avogadro's Hypothesis was a radical statement at the time and was not widely accepted until fifty years later.

He thought that all matter are made up from the four elements.Also he mentioned that there were four qualites of these elements;moistness, dryness, hotness and coldness.
Ernest Ruderford
We can understant that proton number is important for nucleus because it can changed properties of nucleus
Bohr's atomic model
by: Efe Suner
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