The chemical formula for an emerald is Be3Al2(SiO3)6. An emerald can be described as:

• A. an alloy
• B. a compound
• C. an element
• D. a mixture

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the definitions of the terms involved. An element consists of only one type of atom, a mixture contains two or more substances physically combined, an alloy is a mixture of metals, and a compound is a substance formed when two or more elements chemically combine in fixed proportions.
2. Step 2: Analyze the chemical formula of emerald, which is Be3Al2(SiO3)6. This formula shows that emerald contains beryllium (Be), aluminum (Al), silicon (Si), and oxygen (O) atoms chemically bonded together in a fixed ratio.
3. Step 3: Since the atoms are chemically bonded in a specific ratio, emerald is not a mixture or an alloy, which are physical combinations without fixed ratios or chemical bonds.
4. Step 4: Because emerald contains more than one type of element chemically combined, it cannot be classified as an element.
5. Step 5: Conclude that emerald is a compound, as it is a pure substance made of two or more elements chemically bonded in a fixed proportion.