--> None reactive elements such as noble gases( helium, argon, krypton, xenon and radon) exist as individual atoms which, thus they are monoatomic elements.

--> Elements such as halogens exist in the air as

diatomic molecules -> combination of two atoms

--> Made up of ions ( electrically charged particles) which carry either positive or negative charges

--> cannot be separated through physical methods

(composition)

~A compound contains two or more element chemically combined in a fixed ratio.

~The smallest particle in a compound is a molecule of an ion.

(Decomposition)

~A compound can be broken down into element or simple compounds by thermal decomposition or electrolysis .

--> shows the atoms in the compound

--> shows ratio of the different atoms present in the compound