AZ Chemistry

5 Democritus Theory of Atoms – Structure – Model – Development

Democritus is one of the most influential people in the chemistry. He was the first person who discovered the theory of atom. We know his discovery as Democritus theory of atoms. This theory is one of the most important theory in the atomic theory and organic chemistry in general. His theory has effectively given the great foundation to understanding about atomic.

Democritus theory of atoms successfully motivated other scientists to conduct other experiments and researches in atomic field. This article will cover the principles in Democritus theory of atoms, Democritus history, and other basic atomic theory.

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Democritus Life Biography

We recognize Democritus as great philosopher in the history. He was born in Greece at 460 BC. He had lived for 90 years. He began his journey as philosopher by studying natural philosophy in Thrace, Athens and Abdera, Greece. Aside from philosophy, he also put interest in the geometry study. He enjoyed traveling in many places including Egypt, Babylon and India. One of his popular mentor is Leucippus.

He was the one that inspired Democritus to make atomic theory. We mentioned this part on the previous section. He started to discover atomic theory from simple experiment in cutting stone. Democritus tried to cut stone in half and then he found out that each half of stone had the same properties as the full stone. Then he believed that if you keep cutting that stone into smaller piece, you’ll find out that that stone part is extremely small until you can not see that parts again.

Then he called this very small and invisible parts as atomos. Atomos means invisible in the Greek language. He also pointed out that these atomos are unique based on its matter. He gave example that the atoms of stone have different characteristic and properties with atoms of fur.

Basic Principle – Democritus Theory of Atoms

The Democritus theory of atoms generally consists of 5 basic principles. Here’re some principles from Democritus atomic theory:

Every matter contains the invisible parts named as atoms
Atoms can not be destroyed
Atoms are in solid form, but we are not able to see them
Atoms are similar to each other
Atoms have different properties in terms of size, form, weight, position and type of arrangement.

In this theory, Democritus also described the basic properties of atoms in different type of matter as follow:

In the solid matter, atoms are small and in the pointy form
In the liquid matter, atoms have larger size and round form
In the oil matter, atoms are in well-constructed form, smaller in size

In Democritus theory of atoms we can learn that the matter consists of atoms, the invisible parts, and the empty space or void. Democritus mentioned that atoms can not be destructed nor changed. He also stated that every atom is similar to each other which means that atom has no internal structure. The atomic model of Democritus theory is in solid form. Atoms will have different kind of size, construction, location, weight and arrangement. Between the atoms, there’s void which surround them.

You may also read: Development of Atomic Theory

Democritus & Leucippus Theory

In making the concept of Democrtius theory of atoms, he had many inspiration from his own teacher, Leucippus. Leucippus is the author of famous book, Big Cosmology. Besides Leucippus, Democritus also mentioned that Aristotle inspired his idea about atomic structure. Even though Aristotle fought against the concept of atomic theory, but his basic concept about matter have given the good foundation for Democritus to create his atomic theory.

Democritus revealed the fact that Leucippus has discovered that the atoms have infinite numbers. They are also can not be seen by our eyes. Atoms could move in the empty space or void. He stated that atoms can join to each other and then they will construct the object which can we see. This object can be destroyed if we separate the atoms away.

Even though this Democritus theory of atoms is the mix between Democrtius and Leucippus, we only know Democritus as the creator for this theory. Until now, we can’t actually distinct the contribution of Democrtius and Leucippus in this theory.

Rejection from Aristotle and Plato

Aristotle and Plato are both one of the greatest and most influential philosopher in the world’s theory. Greek philosopher at that period tried to discover the natural world. They did the experiment and study about every phenomena in this world. They also put effort to explain the matter. At that time, both Aristotle and Plato rejected the Democritus theory of atoms.

Aristotle believed that the Empedocles theory is the right one. Empedocles previously stated that all maters are constructed by 4 elements which are fire, air, water and earth. Every matter has the different ratio of these 4 elements depending on the characteristic of that matter. Aristotle then implied that these 4 elements are able to be transformed to each other.

Because Aristotle was really influential at that time, almost people at that time followed the Aristotle belief in Empedocles theory. Because of Aristotle, the Democritus theory of atoms should wait for 2000 years to be rediscovered by other scientists.

Weakness of Democritus theory of Atoms

As the first atomic theory in the world, Democritus theory of atoms should have many flaws. Some basic weakness of this theory include:

1. Democritus was not able to describe atomic model in detail.

On his theory, Democritus only stated that atoms are in the solid form in the void sphare. We can not describe the internal structure of the atom itself. We now know that Atoms consist of 3 parts which are proton, neutron and electron.

2. Democritus can not explain the chemical properties in atom

Since it was the first atomic theory, we could understand that he was not able to include chemical properties to his discovery. He only mentioned that atoms have similar properties if they are in same matter. Refer to Democritus theory, atoms in stone must have same properties. While stone’s atoms will differ with fur’s atom. He only discovered the size, shape, arrangement and other physical properties of atoms. But he didn’t mentioned the chemical characteristic in atoms

3. Democritus didn’t include chemical reactions

Another basic weakness of Democritus atomic theory is the fact that he didn’t mention chemical reactions in atoms. He only stated the physical model of atoms. We know later that chemical reactions between atoms are really important in chemistry study. On the following years, scientists were trying to discover chemical reactions in the atom and matter.

You may read: Proton, Electron, Neutron

Dalton’s atomic theory

After great invention of Democritus, In 1803 Dalton made the newer concept of atom. His theory has five basic principle as following points:

All mater contains very small particles which are called atoms. He belived that atoms has the small shape and solid spheres form. He also said that atoms have various motions
Atom can not be destructed and changed. The atoms in element can not be created, destroyed, divided or transformed. He used the Antoine Lavoisier theory to support this point
The weight of atom determines the characteristic of atom. Dalton believed that all atoms in the same element must have same weights. Every single atoms in oxygen is same to another. While atoms in the different element will have the different characteristic from one to another.
Atoms combine in the small and whole-all rations in chemical reactions. Based on Dalton’s experiment, he concluded that the chemical reactions will occur based on atom to atom ratios
Atoms may combine in more than one-all ratios in element reactions. There were multiples number ratios in various compounds like oxygen compound.

You may also read: Postulates of John Dalton

Atomic Theories and Scientist after Democritus Era

Democritus theory of atom was the ancient theory. After Democritus era, the development of chemistry knowledge of atom had growth and more new scientist wrote new theories and experiments. Meanwhile, here are more inventions of atomic theories.

1. Thompson & Rutherford Theory

Following the basic idea from Democritus and Dalton, some great scientist found out the better and detailed theory about atoms. Here’re some atomic theory after Democtritus theory of atoms. In 18977, J.J Thompson successfully discovered the electron part in the atom. He did the experiment using the cathode ray. He represented the cathode rays as the negative charge. Based on this experiment, he released the concept of atom model as the plum pudding. The raisins represented the negative charge electron while the dough represented the positive charge of atom.

Ernest Rutherford, in 1911, performed the experiment using the alpha particles. He shoot the alpha particle through the gold foil. This experiment resulted that most of the alpha particles passed through the gold foil. However, there were few alpha particles which are deflected back. Rutherford believed that there were the positive charge nucleus. in the center of atom and negative charge electron around the nucleus.

You may also read: Louis de Broglie Quantum Theories

2. Bohr Theory

Neils Bohr made the new atom model in 1913. His theory consists of some principles like Electrons are located in the certain orbits around the atom’s nucleus. These orbitals are stable. Bohr called these parts as the stationary orbits

Every orbit has the energy level. The differnt orbit will have the different level of energy. The orbit nereast the nucleus, as an example, will have the different energy level with the another orbit
There are energy transfer in electron’s move. 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 difference of orbit energy level determines the energy and frequency of light which is emitted or absorbed

After these theory, we then learn other atomic theories which details these atomic models. Based on this article, we understand that Democritus’s finding in atomic theory is really useful for chemistry study. He gave the basic principle about atomic model. Even though Democritus theory of atoms has many flaws and wrong statement, we should thank Democritus for opening the door to understand atomic model.

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