Category: Class 9

Discovery of Electron, Protons, And Neutron

Electron: Long tome ago in 1859, WilliamsCrookes and juliusplucker started the study of conduction of electricity through gases at low pressure in discharge tube. After that in 1897, The J. J. Thomson’s used a cathode ray tube to deduced the presence of negatively charged particle that is electron. Experiment: ray tube pass electricity through a […]


Isobar Such atom of different elements which have different atomic number but same mass number is called isobar. The word isobar come from Greek that means Iso- means same and bar- means weight. As they have different atomic number they contain different Number of protons as well as electron. Further they have same mass number […]


Isotope The isotope are the atom of same element which have same atomic number but different mass number. OR Atom of the same elements having same number of protons but different number of neutron. Atomic number: Atomic number is The number of protons present inside the nucleus of atom. Atomic mass: Atomic mass is number […]

Arrangements or Distribution of electron

The arrangement or Distribution of electron in the atom The distribution or arrangements of electron in different shell of the atom is called electronic configuration Of the elements. The arrangements of electron in different shell should be such that it should have Maximum stability. Thus to write electronic configuration of an element, we should know […]

Bohr model atom

To explain stability of the atom Niel Bohr a Danish physicst in 1913 proposed new model of atom. The most important concept of this model of atom was that electron revolves only in certain fixed orbitsaround the nucleus without losing energy in the form of radiation. Example: Solar system; It appear some what like this,  […]

Rutherford model atom

Rutherford model of an atom Around the year 1911, A British physicist Ernst Rutherford carried out the famous gold foil experiment. He did this to understand structure of the atom the experiment was carried out by Rutherford along with Hans Geiger and Ernest Marsden.  The experiment he performed  was the breakthrough in the  field of […]

Thomson model atom

Thomson model of an atom: J. J. Thomson was the first one to proposed model for structure an atom in 1904. In this model J. J. Thomson said positive charge protons and negative charge electrons are arranged in sphere like plum in a sphere Christmas pudding ,where dry fruits embedded or pudding in it, So […]

Structure of Atom

Structure of an Atom First atomic theory given by the John Dalton’s it said  that “All matter is composed of small indivisible particles called Atom.” Atom are the building blocks of the matter. Atom are neither be created nor destroyed, this implies that during the chemical reactions. No atom are destroyed and nit created. It […]