Which of the following best describes the difference between elements and compounds?

• A. Compounds are pure substances, but elements are mixtures of atoms.
• B. Elements can be separated into simpler substances by chemical means, while compounds cannot.
• C. Elements always exist as molecules, while compounds exist only as ions.
• D. Elements consist of only one type of atom, while compounds are made of two or more different elements chemically combined.

Answer: (D)

Verified step by step guidance

1. Understand the definition of an element: An element is a pure substance that consists of only one type of atom. It cannot be broken down into simpler substances by chemical means.
2. Understand the definition of a compound: A compound is a pure substance formed when two or more different elements are chemically combined in fixed proportions. Compounds have properties different from the individual elements that compose them.
3. Recognize that elements are the simplest form of matter and cannot be decomposed into simpler substances by chemical reactions, whereas compounds can be broken down into their constituent elements by chemical means.
4. Note that elements can exist as single atoms or molecules (like O2), but the key distinction is that they contain only one type of atom, while compounds always contain two or more different types of atoms bonded together.
5. Evaluate the given options by comparing them to these definitions to identify the statement that correctly distinguishes elements from compounds.