Which of the following is a key chemical property that distinguishes an element from a compound?

• A. An element always contains more than one type of atom, while a compound contains only one type.
• B. An element cannot be broken down into simpler substances by chemical means, while a compound can.
• C. Elements are always gases at room temperature, while compounds are always solids.
• D. A compound has a variable composition, while an element has a fixed composition.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the definitions of elements and compounds. An element is a pure substance consisting of only one type of atom, while a compound is a substance formed when two or more different types of atoms chemically bond together.
2. Step 2: Recognize that a key chemical property is related to how substances can be broken down. Elements cannot be broken down into simpler substances by chemical means because they are the simplest form of matter.
3. Step 3: In contrast, compounds can be broken down into their constituent elements through chemical reactions, such as decomposition or electrolysis.
4. Step 4: Evaluate the given options based on these definitions. The correct distinguishing property is that an element cannot be chemically broken down further, whereas a compound can be decomposed into simpler substances.
5. Step 5: Note that other options are incorrect because elements can be solids, liquids, or gases at room temperature, compounds have fixed compositions (definite ratios of elements), and elements contain only one type of atom, not more than one.