Atomic theory is one of the most basic and important study in the chemistry. Atomic theory gives the basic understanding about atomic structure which also presents the properties of chemical element and matter. There many atomic theory which are very influential not only for chemistry theory, bu also to other studies like biology, physics, mechanical and many others. One of the modern atomic theory is the atomic theory by Louis de Broglie.

He discovered the new version of atomic model in the Louis de Broglie quantum theory. This theory has strong relation with other previous atomic theory, especially the atomic theory from Bohr. His quantum theory is also the great addition to modify the previous mechanical quantum theory. This article will cover the basic concept of Louis de Broglie quantum theory, its history and other important atomic theories.

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**Louis de Broglie Brief History**

Louis de Broglie can be considered as on of the influential person in the physics and chemistry study. He was born in France in 1892. He was the Professor in the Sciences Faculty at Paris University. He worked in France to perform research about general physics, including quantum theory.

Louis de broglie attended Lycee Janson of Sailly to get his science degree in physics. He ever lived in the war period in 1914-1918. At that time, he still kept his interest in science by learning some technical problems at the Eiffel Tower. He discovered his quantum theory in the 1924 in his thesis for doctor’s degree.

In performign this quantum theory, he greatly affected by the dualism properties of light theory. Before de Broglie, Einstein mentioned that the short wavelength of light can be observed as it consists of some particles. Then, Louis de Broglie successfully discovered the dualism in the matter. After discovered the quantum theory, in 1929 Louis de Broglie received his first Nobel Prize for Physics. He was recognized for his discovery in electrons’s wave nature.

**Principles of Louis de Broglie Quantum Theory**

Louis de Broglie developed his theory in 1929. In his hypothesis, he stated that electrons have the properties of particles and waves. He came up with this thought after the discovery of dualism in light previously. Light posses the dual properties as particle and wave. Louis de Broglie then believed that matter or electrons might act just like light. He mentioned that electrons create the waves in certain orbital around the nucleus. He called this wave as standing wave.

Standing wave has its own energy, frequency and wavelength. In his research, he tried to find out the wave properties of the matter to add the particle properties in that matter. Louis de Broglie stated that the standing waves produced by electrons has the relation with discrete wavelength. The properties of de Broglie’s electrons wave will be covered in the next section of this article.

At that time, de Broglie quantum theory gained great popularity and recognition from influential figure at that time, including Albert Einstein. This quantum theory also made Louis de Broglie to get his Nobel Prize for Physics in 1929.

## 1. Electron Motion Waves

Louis de Broglie quantum theory successfully explained some questions about the previous atomic model, especially about the electron movements. From the experiment before, we knew that electrons moved around the nucleus in the path called orbits.

However, there were some restrictions to these electron movements and electron orbits. Then, Luois de Broglie quantum theory was able to give the answer to this question at that time. The standing wave made by electrons during its movement is the cause of those restrictions. The wave of electrons must have shape which doesn’t fit the atomic boundaries.

This wave will interfere and cancels out which create such a restriction in electron motions and orbitals. This quantum theory also gave the newer atomic model which answered the flaws of Bohr’s atom theory. Louis de Broglie quantum theory gave such a strong impact to the atomic theory and chemistry in general. This theory also greatly contributed in the physics study, especially in the quantum physics study.

## 2. Louis de Broglie & Bohr Atom Theory

Previously, there were some popular atomic theories conducted at that time. Before de Broglie theory, there were Democritus, Dalton, Thompson, Rutherford, Bohr and other scientist who performed the study about atomic model. The Lious de Broglie quantum theory could showed some points to correct the Bohr’s atomic model. Bohr released his atomic theory in 1913.

This Bohr’s atomic model had some flaws which could not explain some detailed properties in atomic especially in electron motions and orbitals. Louis de Broglie then answered some questions in the Bohr’s atomic theory. Here’re the correction of Bohr Atomic theory by Louis de Broglie quantum theory:

**Standing Wave**

Previously, Bohr described that electrons move in the circular shape orbital around the nucleus. Louis de Broglie then explained that this electron path is not orbit. It was the complicated standing wave patterns which are produced by electrons during their movements. The dualism of matter could explain the properties of particle and wave in the electrons in atom.

**Stationary Orbits**

Bohr stated that there ares certain electron orbitals which are stable. He called these orbits as stationary orbits. This point is actually true, but Bohr could not explain in detail about orbit stability at that time. Louis de Broglie theory then could prove that there are standing wave patterns (instead of orbital) which are stable. He could explain this restriction with its relation to the electron wave properties.

**Energy Transfer in Electron Motions**

Bohr said that electron will absorb the energy when it moves form the lower orbit to higher orbit. In contrast, electron will emit the energy when it moves from higher orbit to lower orbit. The energy form is actually the light. This point is nearly true, but we now understand that electrons don’t move from one orbit to another obit. Instead, electrons move from stable standing wave pattern to another standing wave patterns. Louis de Broglie described this phenomena as resonant coupling.

Bohr’s atomic theory was not wrong, it was only nearly true. Louis de Broglie is the one who successfully answered some major questions in the Bohr’s atomic model. He could explain why there were only certain orbits which contain electrons. Albert Einstein also mentioned that de Broglie was successful in explaining the Bohr’s atomic model in detail.

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## 3. Four Quantum Numbers

In the following years, chemists could conduct another theory of atomic model. One of the useful theory about atomic theory is quantum numbers. These quantum numbers are the properties which describe the electrons distribution within the atom. In the atomic quantum numbers, we will learn about principle quantum number, secondary quantum number, magnetic quantum number and spin quantum numbers. Here’re the explanation of these numbers:

**Principal Quantum Number (n)**. It’s the number which explains the main energy level of electron. Principle quantum number is also known as the electron shell. The principal quantum number always has the positive integer such as n= 1, 2, 3, 4, 5, and so on**Secondary Quantum Number (l)**. Secondary quantum number describes the energy sub-level of electron. We also know this as the type of electron orbitals. The numbers of secondary quantum depend on the principal quantum number. The maximum value of secondary quantum number is*n-1.*Secondary quantum number has another term of azimuthal or subsidiary.**Magnetic Quantum Number (ml)**. This term describes the amount of possible orientations for every orbital type. We know that secondary quantum number defines the electron orbital type, so the number of magnetic quantum will depend on the secondary quantum number. The value of ml has ranges between -l to +l. So, if l : 2, so the ml would be -2, -1, 0, 1, 2.**Spin Quantum Number (mS).**This numbers represent the possible two orientations of an electron if there’s effect of magnetic field or another electron which is located on the same orbital. There’re only two electron which are able to occupy the same orbital. They should possess opposite spins. In this condition, we will have the pair of electrons. The value of spin quantum numbers are +1/2 and -1/2.

You may also read: Proton, Electron, Neutron – Proton Uses

### Applications of Louis de Broglie Quantum Theory

As we mentioned before, Louis de Broglie quantum theory gave the strong impact to many studies especially in physics and chemistry. His discovery were the basic principle used for the conducting the research about wave mechanics theory.

This quantum theory obviously enhanced our understanding about physical nature in the atom scale. In the chemistry study, this quantum theory can give the basic information for predict the different type of hydrogen element. With this theory, scientist conducted experiment that showed hydrogen could be in two kinds based on their nucleus’s angular momentum orientation. We can see the applications of Louis de Broglie quantum theory in popular tools like laser, computer / microprocessor, microscope and other micro-electronic devices.

Four quantum numbers explain the arrangement of electrons within the atom. These above numbers describe the probability of electrons distribution in atom. They can actually define the exact position of electrons in atom. You can get the probability distributions by knowing the secondary quantum number (l) and magnetic quantum number (ml). While you can get the potential energy of electron by finding out their main quantum number (n) dan secondary quantum number (l). Meanwhile, that is the Louis de Broglie Quantum Theory in chemistry knowledge.

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