What is the definition of an element?

What is the definition of an element?

• A. A substance that cannot be broken down into simpler substances
• B. A mixture of two or more substances
• C. A substance that can be broken down into simpler substances
• D. A compound formed by identical atoms

Answer: (A)

An element is a pure substance that cannot be broken down into simpler substances by chemical means. This captures the idea that elements are made of one kind of atom and chemical reactions just rearrange atoms or form compounds, rather than splitting atoms apart. If a substance can be decomposed into simpler substances by chemical reactions, it isn’t an element but a compound (or a mixture, if the components aren’t bonded). The option describing a mixture is not an element, and the one about a substance that can be broken down into simpler substances fits a compound, not an element. A molecule formed by identical atoms, while it represents an element in molecular form (like O2), isn’t describing the defining property of an element; the key point is the inability to decompose by chemical means.

An element is a pure substance that cannot be broken down into simpler substances by chemical means. This captures the idea that elements are made of one kind of atom and chemical reactions just rearrange atoms or form compounds, rather than splitting atoms apart. If a substance can be decomposed into simpler substances by chemical reactions, it isn’t an element but a compound (or a mixture, if the components aren’t bonded). The option describing a mixture is not an element, and the one about a substance that can be broken down into simpler substances fits a compound, not an element. A molecule formed by identical atoms, while it represents an element in molecular form (like O2), isn’t describing the defining property of an element; the key point is the inability to decompose by chemical means.