What is an example of a compound?

Water is a prime example of a compound because it is formed from the chemical combination of two different elements: hydrogen and oxygen. In a water molecule, two hydrogen atoms are bonded to one oxygen atom (H2O). This bonding alters the properties of the elements involved, resulting in a substance that has characteristics distinct from either hydrogen or oxygen alone.

In contrast, oxygen (a diatomic molecule, O2) is a pure element that consists of two oxygen atoms bonded together. Air is a mixture of various gases, primarily nitrogen and oxygen, and does not qualify as a compound since it does not consist solely of a fixed composition of chemically bonded elements. Gold is a pure element, represented by the symbol Au, and does not combine with other elements to form a compound in its natural state. Thus, water stands out as the correct example due to its composition and the nature of its chemical bonds.