When two or more different kinds of atoms or elements join together chemically, they form a compound. A compound is a substance composed of atoms of different elements bonded together in specific ratios. These atoms combine through chemical bonds to create a new substance with unique properties.
Compounds are formed through chemical reactions, during which atoms interact and rearrange their outermost electrons to achieve a more stable configuration. The resulting compound has different chemical and physical properties compared to the individual elements that form it.
For example, when one atom of oxygen (O) chemically combines with two atoms of hydrogen (H), they form a compound called water (H2O). Water has distinct properties, such as its liquid state at room temperature, boiling and freezing points, and ability to dissolve many substances, which are different from the properties of oxygen gas (O2) and hydrogen gas (H2) individually.
The formation of compounds is governed by the rules of chemical bonding, including ionic bonding, covalent bonding, and metallic bonding, depending on the nature of the elements involved and their electron-sharing behaviors.