CBSE Class 9 Answered

An atom is the basic type of particle that makes up matter, anything that has mass and occupies space. It is the smallest part of a chemical element, which has the properties of that element. If atoms are taken to be ball-shaped, they have diameters of about 10^-8 meters. They have masses around 10^-23g.

molecule is the smallest amount of a chemical substance that can exist. If a molecule were split into smaller pieces, it would be a different substance.Molecules are made up of atoms that are stuck together in a particular shape. Not all combinations of atoms are possible; atoms like certain shapes, but not others. For example, oxygen atoms always have two bonds with other atoms, carbon atoms always have four bonds with other atoms, and nitrogen atoms always have three bonds with other atoms.