Question

Challenge: Water is a MOLECULE and a COMPOUND; Oxygen can be a MOLECULE but is not a COMPOUND. Explain why:

Answer 1

Answer:

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 that 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. But, 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, are substances that are molecules but not compounds.

Explanation:

I've been asked something kind of like this before, not exactly though. But,  I hope this answers your question!