What Is Atom, History of atom: Ancient Indian and Greek philosophers were always amazed by the unknown and invisible forms of matter. The idea of the divisibility of matter was expressed in India much earlier, around 500 BC.
What Is Atom
Indian philosopher Maharshi Kanad propounded that if we go on dividing matter, we will get smaller and smaller particles and finally a limit will come when the obtained particle cannot be further divided, that is, it will be the smallest. The particle will remain indivisible.
He called this indivisible smallest particle an atom. Pakudha Katyayama, another Indian philosopher, elaborated on this view and said that these particles are usually found in combined form, giving us different forms of matter.
Atom: The smallest particle of an element that takes part in its chemical reaction is called an atom.
Molecule: The smallest particle of an element or compound that can exist in an independent state is called a molecule.
Difference between molecule and atom
| S.N | Molecular _ | Atom _ |
| 1. | The smallest particle of an element participates in its chemical reaction. | The smallest particle of an element or compound can remain in a free state. |
| 2. | Here electrons are made up of protons and neutrons | or made up of many atoms |
| 3. | Atoms generally cannot exist in a free state | it can live freely |
| 4. | Atoms take part in a chemical reaction almost indivisible and their form is not destroyed. | In a chemical reaction, molecules break down into smaller atoms, which combine chemically to form other types of molecules. |
Fundamental Particles of an Atom: The following are the three particles of an atom.
- electron
- Proton
- neutrons
| fundamental particle | mass (in grams) | Charge | searcher | |
| electron | e | 9.1095×10‐²⁸ | Negative Charge | JJ Thomson |
| Proton | p | 1.6726×10‐²⁴ | Positive Charge | rutherford |
| neutrons | n | 1.6750×10‐²⁴ | Electrically neutral | Chadwick |
Structure of the atom :
Many scientists presented different types of models to explain the structure of the atom, JJ Thomson was the first scientist who presented the first model related to the structure of the atom.
- Thomson’s atomic model
- Rutherford’s atomic model
- Niels Bohr’s atomic model
Thomson’s atomic model
Sir JJ Thomson presented the first atomic model in 1904, it is also called Thomson’s watermelon model.
- An atom is made up of a positively charged sphere and electrons are embedded in it.
- Negative and positive charges are equal in magnitude so atoms are electrically neutral.
But Thomson’s atomic model is absolutely wrong.
Rutherford’s atomic model
Ernest Rutherford presented the model of the nucleus of the atom based on the information obtained from the use of scattering of alpha particles.
- Much of the inner part of Rutherford’s proof is blank because most of the alpha passes through the gold foil without being deflected.
- Very little deviates from its path, which shows that the negatively charged part of the positively charged atom is very small.
- The center of an atom is positively charged, also called Na. Almost all the mass of an atom is inside the nucleus.
- The electron revolves around the nucleus in a circular path.
- The size of the nucleus is much less than that of an atom.
Niels Bohr’s atomic model
To overcome the objections raised on Rutherford’s atomic model, Niels Bohr presented the following concepts about the structure of the atom. To overcome the objections raised on Rutherford’s atomic model, Niels Bohr presented the following concepts about the structure of the atom. has been presented.
- Electrons can revolve only in certain orbits which are called discrete orbits of electrons.
- When electrons move around in the divisible orbit, their energy is not radiated.
What is called an electron?
- The electron revolves around the atom. The mass of the electron is several thousand times less than that of the atom. Traditionally it has a negative charge on it. This is denoted by e-.
- What is a proton?
- A proton is a subatomic particle found inside an atom. It is denoted by p+.
- What are neutrons called?
- Neutron is found inside the nucleus of the atom. It resides in the nucleus of the atom of all the elements. A neutron is a fundamental particle with no charge. It is denoted by n⁰.
Read Also:
Frequently Asked Questions.
What is the smallest particle of matter?
Nuclear
Who discovered the atom?
John Dalton (1803)
Who discovered the electron?
Who discovered the electron?
