What do you mean by a molecule, atomicity, molecule of compounds, and an ion?

A molecule is the smallest particle of an element or a compound capable of independent existence
under ordinary conditions. It shows all the properties of the substance. For example: O₂, H₂

Atomicity: The number of atoms present in one molecule of an element is called the atomicity of that element.
• Monoatomic elements - Helium (He), argon (Ar), ...etc.
• Diatomic element - Oxygen, hydrogen, nitrogen, ... etc.
• Triatomic element - Ozone

Molecules of compounds: Atoms of different elements form molecules of compounds together in definite proportions.
For example- Water - H₂O, Ammonia - NH₃, Carbon dioxide - CO₂

Ion: Charged species formed by losing (or) gaining electrons are known as ions. Ions may
contain a single atom or a group of atoms. Ions are two types based on the nature of the charge carried by them.
a. Cation: An ion having a positive charge on it is known as a cation. For example: K⁺, Ag⁺, Pb⁺², etc.
b. Anion: The ion having a negative charge on it is known as an anion. For example: Cl^-, O^-2, etc.