In this section, we explore the concept of molecules, defined as the smallest particle of an element or a compound that retains all the properties of that substance and can exist independently. Molecules are formed by two or more atoms that are chemically bonded together. We differentiate between molecules of elements, which consist of identical atoms (like O₂ for oxygen), and molecules of compounds, which contain different types of atoms (such as H₂O for water).
The atomicity of molecules, which refers to the number of atoms present in a molecule, is also discussed. For example, monatomic molecules have one atom, diatomic molecules have two (like O₂), and polyatomic molecules can have many atoms.
Moreover, we emphasize the role of ions and charges in forming compounds, noting that compounds composed of metals and non-metals contain charged species called ions. Understanding molecules is crucial to comprehending the broader principles of chemistry, as they serve as the building blocks of matter.