Atom in its orbit Atomic Physicists and Physics

The ten famous physicists who built Atomic Physics

DemocritusDemocritus J.J. ThomsonJJ Thomson RutherfordRutherford PlanckPlanck A. EinsteinEinstein
BohrBohr De BroglieDe Broglie SchrodingerSchrodinger PauliPauli DiracDirac


What's Atomic Physics ?

It is Physics which deal with electrons around a nucleous in a atom. The field of Atomic Physics is between Chemistry and Nuclear Physics.Lasers and flueresecence are, for instance, fields of Atomic Physics.

Leucippus and Democritus (Born: about 460 BC in Abdera, Thrace, Greece Died: about 370 BC)
More About Democritus

Leucipeus is the founder of the Atomisism. With Democritus, They gave speculations about the microscopic structure of matter.
Consider a small object, if it you cut it in half, then cut it in half again till the finite state where the division is not possible, you will obtain the smallest part of the object called the atom.

JJ Thomson (Born on December 18, 1856, near Manchester, died in 1940)
JJ Thomson
More About JJ Thomson

JJ thomson had thought that the atom was like a pulm ( or raisin) pudding, where the pudding was positive charges and raisin electrons. This is the first atomic model that it doesn't work at all.

Ernest Rutherford (Born on August 30, 1871, in Nelson, New Zealand died aged 66 on the 19th of October 1937)
More About Rutherford

Rutherford did with his colleges experiments relating to jj Thomsn's model. Using alpha particles that stroke a gold foil, It came out that the incident particles had a small amount of deflections and even some particles returned from the target.
The conclusion was that the atom is made up of the positive nucleus and electrons where the biggest part is simply a vacuum. This second model gave a good understanding about the atom.

Max Planck (Born: 23 April 1858 in Kiel, Schleswig-Holstein. Died: 4 Oct 1947 in Gottingen, Germany)
More About Max Planck

Planck worked very hard to derive a description of the exchange of energy in a system, naimly in the blackbody. He explained how to avoid the ultraviolet catastrophe. He discovered that there is an elementary energy called quantum which by energy is built. Every quantum depends only on its frequency, and the involved constant is called The Planck's constant .
This is what is known by the quantization of energy. Which means the energy is not continued. It's a certain number of quantum , That is quanta. Think of a mountain of sand : mountain is energy and sand is quanta.

Albert Einstein (Born: 14 March 1879 in Ulm, Germany Died: 18 April 1955 in Princeton, New Jersey, USA)
More About Albert Einstein

Einstein discovered the photoelectric effect which is related to the fact that to extract an electron from an atom, one needs the work of the extraction. The remaining energy is given to the moving elecron.The required work is not dependant to the intensity of the incident light but to its frequency of the grain of the light that is the photon. Each photon carry out an energy equal to its frequency times the Planck Constant.

Niels Bohr (Born: 7 Oct 1885 in Copenhagen, Denmark Died: 18 Nov 1962 in Copenhagen, Denmark)
More About Niels Bohr

Using the Rutherford model and the Planck's idea, he applied the quantization principle to the angular momentum of the electron in its orbit in order to derive the radius, the velocity and the energy expressions of the electron in the atom with respect to the quantum number of the electron. Nevertheless, he gave some assumptions to keep the model alive, that is, the electron doesn't radiate in a stable orbit, so it cannot collapse.

Louis de Broglie (Born: 15 Aug 1892 in Dieppe, France Died: 19 March 1987 in Paris, France)
Louis de Broglie
More About Louis de Broglie

De Broglie expanded the wave-matter notion. Every materiel is a wave as well. It's a matter of speed. Think of the harmonics of standings waves in a string tied down at both ends. Here, the circunference of an electron's orbit is equal to an integer times a constant. Some very simple calculations confirme the quantization of the angular momentum.

Erwin Schrodinger (Born: 12 Aug 1887 in Erdberg, Vienna, Austria Died: 4 Jan 1961 in Vienna, Austria)
More About Erwin Schrodinger

The Bohr's model is not sufficient. Schrodinger established its equation to solve the state of the electron in the Hydrogen atom. The quantum number of the Bohr 's model is just the principal one. The Schrodinger's equation gives another one : The orbiltal angular momentum quantum number, which is directly related the first one. This number tells us about the revolution of the electron in the atom around the nucleus,that is the discret values of the angular momentum. From now and then , the electron is not in the Bohr's radius, but it is just the most likely place where the electroncan be found.

Wolfgang Pauli (Born: 25 April 1900 in Vienna, Austria Died: 15 Dec 1958 in Zurich, Switzerland)
More About Wolfgang Pauli

Pauli is essentially known by his priciple, which is called by The exlusion principle; that is, an electron in an orbit can have one and just one state. Every electron in the atom has one and only one state in this atom. In the other hand , two or more electrons cannot be in the same state. This exclusion is due to the thirth quantum number which is the magnetic quantum number related to the spin of the electron, that is its rotation around itself.

P.A.M. Dirac (Born: 8 Aug 1902 in Bristol, England Died: 20 Oct 1984 in Tallahassee, Florida, USA)
More About P.A.M. Dirac

As the Schrodinger's equation doesn't take acount to the relativistic case of the electron in the atom, Dirac devised a sofisticated equation designed for this problem. Let's avoid headaches!

Last modification is done on: 2007-03-16 à 23:38

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