the constituent elements of the molecules the ratio of the number of constituent atoms in them

proton +ve electron -ve

a JJ Thomson b Rutherford c James chadwick

James chadwick

William crookes, JJ Thomson , Rutherford , niels bohr, goldstein

William crookes, conducted experiments by passing electricity at High Voltage through a glass tube in which both side are fixed with metal plates as electrodes as air is an insulator electricity does not pass through the air in the tube at normal pressure. but when the tube was evacuated electricity passed through it a perferated positive electrode (anode) was used , a light green glow was observed on the zinc sulphide coated Glass wall behind it

cathode rays have mass travels in straight path have negative charge get deflect in magnetic field

Rutherford

Rutherford

atom has center called nucleus size of nucleus is extremely small entire positive charge and most of the mass of atom are concentrated in nucleus electrons reward very fast around in nucleus in circular path or orbits

negative charge electrons revolving around the nucleus should continuously loss energy and collapse into the nucleus but this does not happen therefore it is rejected

electrons revolve around the nucleus of an atom in fixed orbits electrons in each Orbit have a definite energy so orbits are also known as energy level as long as electrons revolve in a particular Orbit their energy does not change So known as stationery energy level Orbit can be represented by giving numbers 1234 etc

isotopes are different items of same element having the same atomic number but different mass number