Atoms and molecules are fundamental building blocks of matter, but they have distinct differences. Here are two key differences between atoms and molecules:
Composition: Atoms are the smallest units of an element that retain the chemical properties of that element. They consist of a nucleus containing protons and neutrons, surrounded by electrons. In contrast, molecules are formed when two or more atoms chemically bond together. A molecule can consist of atoms of the same element (e.g., oxygen molecule, O2) or different elements (e.g., water molecule, H2O).
Stability: Atoms are generally stable when they have a filled outer electron shell (except for hydrogen and helium, which have unique stability criteria). Atoms can achieve stability by either gaining, losing, or sharing electrons with other atoms, resulting in the formation of chemical bonds. Molecules, on the other hand, are more stable structures than individual atoms because the bonded atoms share electrons to attain a stable electron configuration. The chemical bonds that hold atoms together in molecules contribute to the overall stability of the molecule.
In summary, atoms are the basic units of elements, while molecules are formed when atoms chemically bond together. Atoms are stable when their electron shells are filled, while molecules achieve stability through the sharing, gaining, or losing of electrons between atoms.