Periodical development of fundamental particles and structure of atoms can be explained from different atomic models .
Explanation:
Periodical development of fundamental particles :
About 2600 years ago an Indian sage called kanada proposed that all forms of matter are composed of very small particles called as Anu and each Anu is made up of smaller particles called Parmanu .
Later Greek philosopher Democritus called these atoms and according to him atoms are indivisible and indestructible .
John Dalton's theory describes elements in terms of atoms which he believed to be indivisible particles.
But Later John Dalton's postulate which suggests that atom is indivisible is disproved by various experiments conducted by various scientists :
1. Electron - J.J Thomson discovered the electron while experimenting with cathode rays in 1897.
2. Proton - Proton was discovered by Gold stein in 1920.
3. Neutron was discoverer by James Chadwick in 1932 by bombardment of alpha particle at beryllium . Structure of atom :
J.J Thomson atomic model : After the discovery of electrons ; he proposed his plum and pudding model which shows that electrons are embedded throughout the positively charged material.Rutherford alpha particle scattering experiment : This experiment lead to the discovery of nucleus . According to this experiment all the positive charge and most of the mass of atom is concentrated in a small core called nucleus . According to this model nucleus is composed of neutrons and protons . Electrons are distributed around the nucleus and occupy most of the volume. Bohr atomic model : Bohr modified Rutherford atomic model of atom by suggesting that electrons move in specific energy levels around nucleus.
Schrodinger's model of atom : This model is most precise model and is used in present days . According to him electrons are present in a particular region or space around the nucleus called as orbitals where probability of finding the electrons are more.
