(a) What is an atom ? How do atoms usually exist?
(b) What is a molecule? Explain with an example.
(c) What is the difference between the molecule of an element and the molecule of a compound ? Give an example of each.
a) Atom is the smallest particle of a chemical element that can exist. Atoms of the most elements are chemically very reactive and do not exist in the free state. So, they usually exist in 3 ways:
1. In the form of molecules:- H2, N2, O2 etc.
2. In the form of an ion:-Cl-, Na+, etc.
3. In the free-form:- Ne, Ar, He etc.
b) A molecule is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up of atoms that are held together by chemical bonds. Examples of such elements are oxygen and chlorine.
c) The only difference between a molecule of a compound and a molecule of an element is that in a molecule of an element, all the atoms are the same. For example, in a molecule of water (a compound), there is one oxygen atom and two hydrogen atoms. But in a molecule of oxygen (an element), both of the atoms are oxygen.