Avogadro’s number is the number of molecules present in:

A. 1 g of molecule

B. 1 atom of molecule

C. 1 mole

D. 1 litre of molecule

Matter and Its Classification

• Matter is anything that occupies space and has mass, hence it possesses the properties of mass and volume.
• Based on physical behavior, matter is classified into solids, liquids, and gases.
• Based on chemical behavior, it is divided into pure substances and mixtures.

Pure Substances

• Pure substances are further classified into elements and compounds.
• Elements consist of groups of the same type of atoms, while compounds are made of atoms of different elements bonded together.
• The atom is the smallest unit of matter, composed of a nucleus (containing protons and neutrons) and electrons revolving around the nucleus in shells.

Atomic Mass

• Everything in the universe is made up of atoms.
• Since the mass of an atom is extremely small and cannot be measured directly, the concept of relative atomic mass is used.
• The standard is taken as the mass of hydrogen (1 unit), and the mass of other atoms is compared relative to it.
• Today, a modern standard is based on the mass of 1 carbon-12 atom, internationally adopted in 1961.

Mole Concept and Avogadro’s Number

• A mole is the amount of substance that contains as many particles (atoms, molecules, or entities) as there are atoms in 12 g of carbon-12 isotope.
• This defines the foundation of physical chemistry.
• The number of particles in 1 mole is called Avogadro’s number, which equals 6.023 × 10²³ entities.
• It is denoted by the symbol Nₐ.

Final Answer

Thus, Avogadro’s number represents the number of molecules present in 1 mole of a substance. Correct option: C