List of the Atomic Theories in Order

Atomic Theory

Atomic theory has evolved since ancient times. The hypothesis of Greek scholars has become the basis of analysis by scientists. They have done a lot of discoveries and theories regarding the atom. Moreover, it derives from the Greek word “atomos,” which means indivisible.

Since then, the scientific community has discovered that these particles further divide into sub-particles called protons, neutrons, and electrons. Nevertheless, the name “atom” has stuck.

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List of Atomic Theories

1. Ancient Greek Beliefs

“All the matter is made up of tiny units called atoms” this was first proposed by Leucippus and Democritus, in the fifth century B.C., that all matter is made of tiny units called atoms.

In addition, they tell that these were solid particles without internal structure, and came in a variety of shapes and sizes. Moreover, they also made some intangible qualities such as taste and color.

2. Dalton’s Atomic Theory

English chemist John Dalton subsequently made on the Greek notion of atoms in 1808. He postulated that matter is made of atoms, which are small indivisible particles. He also proposed that while all atoms of one element are identical, they are totally different from those that make up other elements.

3. J.J. Thomson’s Theory

In 1904, English physicist Joseph J. Thomson proposes the “plum pudding” theory of the divisible atom. He does so after discovering electrons in 1897.

Also, his model suggested that atoms consist of a big positively-charged sphere studded with negatively charged electrons (he called them “corpuscles”) like fruit in a plum pudding.

Furthermore, he put forward that the charge of the positive sphere’s charge is equal to the negative charges of the electrons. Today we call the positive charged particles protons and the negative one’s electrons.

4. Rutherford’s Hypothesis

In 1911, Ernest Rutherford (British physicist) proposed a nuclear model on atoms. An atom in which a nucleus exists. In the past, he discovered the part of activity such as the movement of protons and electrons within the central part of the atom. He further hypothesized that the number of protons and electrons are equals in an atom.

5. Bohr’s Theory

In 1913, Danish physicist Niels Bohr proposed a planetary model, which states that electrons revolve about the nucleus just as the planets orbit the sun. When the electrons are in orbit, they possess “constant energy.”

When these atoms grasp the energy and move into a higher orbit, this theory refers to them as “excited” electrons. At the time of returning to their original orbit, they leave this energy as electromagnetic radiation.

6. Einstein, Heisenberg and Quantum Mechanics

As far as the earlier theories are concerned, the atom consists of a central and heavy nucleus centered by a number of electrons. Earlier theories used to treat electrons, and other tiny particles as fixed solid “lumps,”.

On the other hand, modern quantum theory specifies them as statistical “clouds”. Moreover, one can measure their speed exactly along with their locations. However, we can’t do them at the same time.

Solved Question For You

Question: Explain briefly ‘Quark’s Theory’?

Answer: As scientists looked at atoms with increasingly more powerful instruments, they discovered that the protons and neutrons that made up the nucleus were in turn made of even smaller particles.

In the 1960s, physicists Murray Gell-Mann and George Zweig called these particles “quarks,” borrowing a word used in a James Joyce novel.