What is the difference between an atom and a molecule? Give one example of each.

Atom: The smallest unit of an element that cannot be further divided by chemical means. It may or may not exist independently.

Example: A helium atom (He).

Molecule: Two or more atoms chemically bonded together. Molecules can be of the same element or different elements.

Example: A water molecule (H₂O).

Key difference: Atoms are the basic building blocks, while molecules are formed when atoms join together.