The Discovery of Atomic Structure

Many researchers and thinkers, notably Newton, Galileo, Lavoisier, and Boyle, explored and expanded on the notion of atomic structure and atoms. However, an English scientist, meteorologist and physicist named John Dalton first mentioned that everything is made up of atoms in the book he published in 1808. Moreover, the commonly and a very famously known Dalton’s atomic theory is one of his contributions. And if we speak about the atom Democritus who was a Greek philosopher was the first person to use the term atom. 

Here, in this article, we’ll look at Dalton’s atomic structure and how he found the atomic structure with some other scientists’ models such as the JJ Thompson atomic model, Rutherford atomic model, etc.

Dalton’s Atomic Theory

From 1743-to 1794 Dalton created his theory referring to Antoine Lavoisier’s theory using the conservation of mass and definite proportion reference. It later became the fundamental building block of atomic structure or chemical structure. Dalton claimed that every compound is made up of atoms of a unique, distinct kind, which can unite to build more complicated structures even though they can’t be transformed or damaged chemically or physically.   This was the first scientific hypothesis of the atom, considering Dalton arrived at his findings by testing and empirical investigation of the data.

Dalton came to his conclusion by studying various masses of various elements such as tin, oxygen and their combinations. And found that they show a common pattern in their formation or combinations. And also hypotheses about the difference in masses due to the difference in the atomic structure of the elements.

The main postulates of Dalton Atomic theory :-

• Matter is made up of various tiny invisible particles commonly known as atoms
• An element has similar or identical atoms
• A compound is formulated using a combination of atoms of either the same or different atoms.
• A chemical reaction is simply a combination or rearrangement of various atoms in different conditions.

JJ Thompson Model

JJ Thompson did a cathode ray tube (CRT) experiment in which he found the existence of electrons in the atom.

A cathode-ray tube is a packed tube having a vacuum inside it with a sufficiently needed flow of cathode-ray inside it used by Thompson Similar to the discharge of lightning. In his experiment, Thompson used an anode and a cathode, where the cathode emitted the ray and the anode received it. And he placed two opposite charged electric plates for the rays to get deflected. He found that the rays are getting deflected toward the positively charged plate or away from the negatively charged plate (depicting the deflection of electronics).

To verify it he then used magnets instead of plates, in which he found the mass to charge ratio of the deflected particles which showed the particles that are deflected have very less mass than an atom. After which, he postulated the plum pudding model of the atom in which electrons and protons (the positively charged matter) are unevenly placed in a pudding.

Ernest Rutherford model (Gold Foil Model)

In his experiment, Ernest Rutherford used a gold foil on which he passed alpha beams which are beams from helium nuclei. In the experiment, Rutherford thought that as per Thompson’s model all the alpha particles would pass through the foil. However, he found that most of the alpha particles passed. However, few particles reflected over 90 degrees, depicting the presence of highly dense material at the centre. And based on this he postulated:

• There is a positive charge (nucleus) in the atom which contains most of the mass of the atom. Also, the positive charge has a very minute size in the atom.
•  An atom may have a large amount of space as most of the particles passed with small deviations through it.

Neil Bohr’s Model (Planetary Model)

In his model, Neil Bohr compared the model of the atom with the model of planets and the sun. Where he stated that electrons move centric to the nucleus on a rotational basis like planets around the sun and their path is known as orbit. And each orbit has its energy level or constant energy.

Moreover, every electron can grasp the energy and move to a higher energy level or bigger radii orbit and can lose energy and come back to a lower energy orbit also they can only be in energy levels of orbits having discrete values.

Quantum Atomic Model

According to this model of the atom, the electron is around the nucleus like an electron cloud where most of the electrons are found. The cloud is arbitrary and the exact location of an electron is unknown as they are rapidly moving around the nucleus.

Conclusion

To sum up, the initial fundamental finding on the structure of the atom was done by John Dalton. And he said that atoms are the fundamental building blocks of any compound and the chemical reactions are just rearrangements of atoms. Then in later years JJ Thompson playing with CRTs found the existence of electrons and positively charged particles (neutrons) embedded like a plum pudding model. Further, in subsequent years, Rutherford referencing the Thompson model found the location of the nucleus and electrons using a gold foil experiment. And further, more and more experiments were done and the current atomic structure was developed and was characterised by the modern periodic table.