How is a compound defined?

A compound is defined as a substance that is formed when two or more different elements are chemically bonded together. This definition captures the essence of what makes a compound unique: it consists of distinct elements that are chemically combined in a fixed ratio, resulting in new properties that are not characteristic of the individual elements.

For example, water (H₂O) is a compound made from hydrogen and oxygen atoms bonded together. The chemical bonding involves interactions like covalent bonds, where atoms share electrons, leading to the formation of a stable substance with its own unique characteristics.

While the other options describe other types of substances—such as elements, mixtures, or solutions—they do not meet the criteria for defining a compound. A single type of atom refers to an element rather than a compound. A mixture involves the physical combination of substances without chemical bonding, and a solution refers to a homogenous mixture where solutes are dissolved in a solvent, which does not necessarily involve the formation of new substances through chemical bonds.