Atomic Structure

Atom: The smallest particle of a chemical element that can exist is called an atom. It cannot exist independently without combination with other atoms or molecules. Let us consider the element iron . All the atoms of iron are alike and when comes in contact with water and air, undergoes rusting.

Molecule: The smallest unit, consisting of a group of atoms, into which an element or a compound can be divided without a change in its chemical nature is called a molecule. A molecule can exist independently and consist of one or more than one atom of the same element. Let us consider an example: two hydrogen atom come together to form hydrogen molecule.

   Atom                                  Molecule

1. Cannot exist              1. Can exist independently.

independently.

2. May or may not         2. Stable 

react.           

3. Single atom cannot    3. Group of atoms having 

be further divided.             same or different atoms 

                                         that can be further                                                    broken up into atoms.

4. Example:                    4. Example: 

an atom of hydrogen.      two atoms of hydrogen

                                        combine to form a 

                                         hydrogen molecule.