Is Water a Compound?

Why water is a compound and not an element or just a molecule

Water is a compound consisting of two hydrogen atoms and one oxygen atom covalently bonded together.
Water is a compound consisting of two hydrogen atoms and one oxygen atom covalently bonded together. Dorling Kindersley / Getty Images

Question: Is Water a Compound?

Have you ever wondered whether or not water is a compound? Here's the answer to the question and the explanation for it.

Water as a Compound and Molecule

Yes, water is a compound. A compound forms whenever two or more atoms form chemical bonds with each other. The chemical formula for water is H2O, which means each molecule of water consists of one oxygen atom chemically bonded to two hydrogen atoms.

Thus, water is a compound. It's also a molecule, which is any chemical species formed by two or more atoms chemically bonded to each other. The terms molecule and compound mean the same thing and can be used interchangeably.

Sometimes confusion arises because the definitions of 'molecule' and 'compound' haven't always been so clear-cut. In the past, some schools taught molecules consisted of atoms bonded via covalent chemical bonds, while compounds were formed via ionic bonds. The hydrogen and oxygen atoms in water are covalently bonded, so under these older definitions, water would be a molecule, but not a compound. An example of a compound would be table salt, NaCl. However, as scientists came to understand chemical bonding better, the line between ionic and covalent bonds became fuzzier. Also, some molecules contain both ionic and covalent bonds between the various atoms.

In summary, the modern definition of a compound is a type of molecule consisting of at least two different types of atoms.

By this definition, water is both a molecule and a compound. Oxygen gas (O2) and ozone (O3), for example, would be examples of substances that are molecules but not compounds.

Why Water Is not an Element

Before mankind knew about atoms and elements, water was considered an element. Other elements included earth, air, fire, and sometimes metal, wood, or spirit.

In some traditional sense, you could consider water an element, but it doesn't qualify as an element according to the scientific definition. An element is a substance consisting of only one type of atom. Water consists of two types of atoms: hydrogen and oxygen.

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