Structure of Atom – Notes

Atomic Particles
Matter is made up of atoms that further consist of sub-atomic particles.
Sub-atomic particles are electrons, protons, and neutrons.
Protons are positively charged, electrons are negatively charged and neutrons are neutral.
Protons and neutrons have mass equivalent to a Hydrogen atom whereas electrons has a negligible mass.
Protons and neutrons, together called nucleons, are present in the center of atom surrounded by revolving electrons and other uncommon sub-atomic particles.
In 1808, John Dalton proposed the atomic theory of matter. According to Dalton, an atom is the smallest particle of matter.
The research done by scientists like J.J Thomson, Goldstein, Rutherford, Chadwick and Bohr in the later part of the 19th century and 20th century proved that an atom is not the smallest indivisible particle.

Atomic Models
According to the Thomson Model of Atom, an atom is a sphere of uniform positive charge with negatively-charged electron embedded in it just like plums in a pudding.
The gold foil experiment conducted by Rutherford disapproved Thomson’s model.