______________ was an ancient greeck philosopher studied the nature of the matter and the basic constituents of all substance.

________________ proposed a theory of atom known as the atomic theory.

_____________ gains three electron in its valence shell forming an anion with three negative charge.

Oxygen has_________ isotopes.

_______________ loses two electrons from its valence shell forming a cation.

According to _______________ atomic theory atoms are neither created nor destroyed.

_____________________ is the electronic configuration of nitrogen atom.

According to _______________ atomic theory,matter consists of small indivisible particles called atoms.

_________________ discovered the positive rays emitted the anode.

_______________ discovered that cathode rays have kinetic energy and raise the temperature of a metallic object on which they fall.