Introduction

INTRODUCTION

Matter in the universe is made up of elements
Elements are made up of simple basic units called atoms.
Democritus proposed the earliest theory on atoms that all the matter is made up of tiny particles called atoms.
Early in the 19^th century John Dalton enunciated the Atomic theory.
According to Dalton’s theory Atom is smallest and indivisible particle of matter.
By 1900 it was proved that an atom is not simple but it consists of charged particles electrons, protons and the neutral particles called neutrons.