In the classification of matter, which statement best defines a chemical element?

• A. A substance composed of two or more different elements chemically combined in a fixed ratio.
• B. A physical combination of two or more substances in which each retains its own chemical identity.
• C. A substance that can be separated into simpler substances by physical processes such as filtration or distillation.
• D. A pure substance made of only one type of atom that cannot be broken down into simpler substances by chemical means.

Answer: (D)

Verified step by step guidance

1. Understand that matter is classified into pure substances and mixtures. Pure substances have a fixed composition and distinct properties.
2. Recognize that pure substances can be further divided into elements and compounds. Elements consist of only one type of atom, while compounds contain two or more different elements chemically combined.
3. Recall that a chemical element is defined as a pure substance made up of only one kind of atom, which cannot be broken down into simpler substances by chemical means.
4. Compare the given statements to this definition: the correct statement must describe a substance with only one type of atom and no simpler chemical breakdown possible.
5. Conclude that the statement 'A pure substance made of only one type of atom that cannot be broken down into simpler substances by chemical means' best defines a chemical element.