ATOM(PARAMANU),HISTORY

ATOM- An atom is the basic building block of chemistry. It is the smallest unit into which matter can be divided without the release of electrically charged particles. It also is the smallest unit of matter that has the characteristic properties of a chemical element.

An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms.

MAHARSHI KANADA-Kaṇada proposes that paramanu (atom) is an indestructible particle of matter. The atom is indivisible because it is a state at which no measurement can be attributed. He used invariance arguments to determine properties of the atoms. He also stated that anu can have two states — absolute rest and a state of motion.

                                                   Maharshi kanada

Maharshi Kanad is one of the greatest sage in the history of the Hindu religion.Many believe it was Kanada who originated the idea that paramanu (atom) was an indestructible particle of matter. An interesting story states that this theory occurred to him while he was walking with food in his hand. As he nibbled at the food in his hand, throwing away the small particles, it occurred to him that he could not divide the food into further parts and thus the idea of a matter which cannot be divided further came into existence. He called that indivisible matter anu, i.e. atom.

The atom is considered the basic building block of matter. Anything that has a mass—in other words, anything that occupies space—is composed of atoms. While its name originally referred to a particle that couldn't be divided any more—the smallest thing possible—we now know that each atom is generally made up of smaller particles. Given that these particles make up atoms, they are often referred to as subatomic particles. There are three subatomic particles: protons, neutrons and electrons.

Two of the subatomic particles have electrical charges: protons have a positive charge while electrons have a negative charge. Neutrons, on the other hand, don't have a charge. A fundamental rule is that particles with the same charge are repulsed from each other, while particles with opposite charges are attracted to each other. So, much like opposite ends of a magnet, protons and electrons are attracted to each other. Likewise, just as when you experience resistance trying to push the same ends of two magnets together, protons are repelled from other protons and electrons are repelled from other electrons.

The History of Atomic Theory:-

The first person to propose that everything on Earth is made up of tiny particles was the Greek philosopher Democritus, around 450 B.C. He used the term atomos, Greek for “indivisible,” from which the modern term “atom” is derived. His idea was not taken seriously at the time, however, and it was many centuries before the concept of the atom would be revived. In the 19th century, John Dalton proposed the atomic theory that is still largely correct today. He put forth five postulates to explain how atoms made up the world around us: (1) all matter is composed of infinitely small particles, or atoms; (2) all atoms of a given element are identical to one another and (3) are different from the atoms of all other elements; (4) two or more elements can combine in a fixed ratio to form a compound; and (5) atoms cannot be created or destroyed in a chemical reaction, but they can be rearranged to form new substances.

Discovering the Subatomic Particles that Make up the Atom:-

Dalton was only partially correct about the particles that make up matter. While atoms cannot be broken down further by ordinary chemical or physical processes, they are composed of three smaller subatomic particles. The first clue about the subatomic structure came at the end of the 19th century when J.J. Thomson discovered the electron. Scientists knew that the overall charge of an atom was neutral, but Thomson’s “plum pudding model” of the atom attempted to reconcile this new information regarding the existence of a negatively-charged particle, suggesting that electrons were found studded throughout an area of positive charge. Just a few years later, Ernest Rutherford performed an experiment showing that most of an atom’s mass is concentrated in the nucleus, where protons account for an atom’s positive charge, and the tiny negatively-charged electrons make up most of the space outside of the nucleus. This disproved Thomson’s plum pudding model and brought scientists one step closer to the familiar model of the atom we know today. The neutron was discovered later, in 1932, by James Chadwick. This final piece of the puzzle meant that scientists had now accounted for all the mass present in an atom with protons and neutrons, and all of its charge with protons and electrons.

The Structure of an Atom:-

Protons are found in the nucleus of an atom, have a positive charge, and a mass of one atomic mass unit (AMU) each. The number of protons is equal to the atomic number on the periodic table and determines the identity of the element. Neutrons are also found in the nucleus. They have no charge, but they have the same mass as protons and thus contribute to the atomic mass of an atom. Electrons orbit around the nucleus in clouds. They have a negative charge and negligible mass, so they contribute to the overall charge of an atom, but not to its mass.

The tiny atomic nucleus is the center of an atom. It constitutes positively charged particles “PROTON” and uncharged particles “NEUTRON.” On the other hand, the extra nucleus part is a much larger region. It consists of a cloud of negatively charged particles called an ELECTRON. Electrons revolve in orbit around the nucleus. The attraction between the protons and electrons holds the structure of atom together.