Which of the following best describes an element?

• A. A mixture of two or more different atoms bonded together.
• B. A substance that cannot be broken down into simpler substances by chemical means.
• C. A substance composed of molecules containing different types of atoms.
• D. A compound formed by the combination of two or more elements.

Answer: (B)

Verified step by step guidance

1. Understand the definition of an element in chemistry: An element is a pure substance consisting of only one type of atom and cannot be broken down into simpler substances by chemical means.
2. Analyze each option given in the problem to see if it matches this definition:
3. Option 1: 'A mixture of two or more different atoms bonded together' describes a compound or mixture, not an element.
4. Option 2: 'A substance that cannot be broken down into simpler substances by chemical means' matches the definition of an element.
5. Option 3 and 4 describe compounds or molecules made of different atoms, which are not elements but combinations of elements.