Man’s curiosity about the universe is limitless. While trying to understand how the world works, we began to ponder into the constituent particles of the matter around us. We began to cut matter into smaller and smaller pieces, from molecules to atoms.
Several physicists and chemists like John Dalton, Neils Bohr, Ernest Rutherford and J. J. Thomson came up with certain theories for the atomic structure of matter, of which some failed to justify their behavior and properties. Atom’s, which were once believed to be the smallest constituting particles of matter proposed by John Dalton with his atomic theory, were found to consist of 3 subatomic particles, each particle with its own distinct properties summing up to a stable atomic structure model. These subatomic particles are :
1. Proton: A positively charged subatomic particle
Mass of proton is 1.6727 x 10-24 g.
For ease of calculations, we use amu (Atomic Mass Unit)[ 1 amu = 1.6605 x 10-24 g ]
So, the mass of proton in amu is 1.007316.
2. Neutron: It is a particle with zero effective charge i.e neither positive nor negative.
Mass of a neutron is 1.6750 x 10-24 g which is 1.008701 amu.
3.Electron: It is the negatively charged subatomic particle
Mass of electron is 9.110 x 10-28 g which is 0.000549 amu.
From the data we can see that,
protons and neutrons have similar masses of 1 amu whereas the mass of an electron is 2000 times lighter.
While explaining about atomic structure, Neutrons and Protons are held together rather closely in the center of an atom. Together they make up the nucleus, which accounts for almost all of the mass of the atom.
Whereas, electrons which are in constant motion around the nucleus, constitute almost the entire volume of the atom.
The negatively charged electron is attracted to the positively charged nucleus by a Coulombic attraction.Whereas, protons and neutrons are held together in the nucleus by the strong nuclear forces.
The chemical reactivity of an element is primarily based on the number of electrons in the atom of that element. The elements reactivity also depends on the effective charge of the atom wherein the effective charge is the sum of number of protons to electrons.
Given below is the atomic structure of an oxygen atom with 8 electrons, 8 protons and 8 neutrons.Here we can see that the electrons occupy the outer shell layers, whereas the protons and neutrons can be found in the nucleus.
Moreover with today’s technology, it has been found that the subatomic particles namely protons, neutrons and electrons have constituent particles, called Quarks and Gluons. Quarks and Gluons are the building blocks for larger particles, but they show varied properties compared to their larger particle counterparts which is a discussion for high level particle physicists.