CHEMISTRY - Atoms and Molecules

<b> Atom :-</b> An atom is the smallest particle of an element which may or may not be capable of independent existence. For ex. Atoms of iron , copper, silver, gold etc. Can exist freely whereas atoms of hydrogen, oxygen , nitrogen etc. cannot exist freely.

<b>Molecule :-</b> A molecule is the smallest particle of an element or a compound which can exist freely.

* Molecules of elements :- As they are made up of only one kind of atom , they are called homoatomic or homonuclear molecules.

* Molecules of Compounds :- They are made up of atoms of different elements and hence are called heteroatomic or heteronuclear molecules. They may be diatomic, triatomic etc. Depending upon the number of atoms present in one molecule of the compound.

<b> Mixtures :-</b> A material containing two or more subsstances ( elements or compound ) in any proportion is called a mixture. The properties of a mixture are the properties of its constituents. Further, a mxture can be separated into its constituents by simple physical method. Mixture are further classified as :-

1. Homogeneous Mixture :- A mixture is said to be a homogeneous if its composition is uniform throughout.

2. Heterogeneous Mixtures :- A mixture is said to be a heterogeneous if its composition is not uniform throughout.