CBSE Class 11-science Answered

Atom:

• The smallest particle of an element is called as an atom.
• Further division of an atom is impossible.
• It consists of nucleus and electrons revolving around nucleus. The nucleus consists of protons and neutrons.
• For example: Hydrogen atom consists of a nucleus having one proton and an electron revolves around the nucleus.

Molecule:

• Two or more atoms combine together to form a molecule.
• Molecule can further be divided into the atoms from which it is formed.
• It consists of two or more like or different atoms combined through covalent or ionic bond.
• For example: The H₂ molecule consists of two hydrogen atoms attached by a covalent bond. The HCl molecule consists of two different atoms namely H and Cl.

An atom may or may not have independent existence while a molecule is capable of having independent existence. For example: oxygen atom cannot exist independently while O₂ is capable of existing independently.