Which of the following is a covalent (molecular) compound?

• A. CO_2
• B. KBr
• C. MgO
• D. NaCl

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the difference between ionic and covalent compounds. Ionic compounds form between metals and nonmetals and involve the transfer of electrons, resulting in ions. Covalent compounds form between nonmetals and involve the sharing of electrons.
2. Step 2: Identify the elements in each compound and determine if they are metals or nonmetals. For example, in CO_2, both carbon (C) and oxygen (O) are nonmetals.
3. Step 3: Analyze each compound: KBr consists of potassium (K, a metal) and bromine (Br, a nonmetal), MgO consists of magnesium (Mg, a metal) and oxygen (O, a nonmetal), NaCl consists of sodium (Na, a metal) and chlorine (Cl, a nonmetal), and CO_2 consists of carbon (C, a nonmetal) and oxygen (O, a nonmetal).
4. Step 4: Since CO_2 is composed of two nonmetals, it forms covalent bonds by sharing electrons, making it a molecular (covalent) compound.
5. Step 5: Conclude that KBr, MgO, and NaCl are ionic compounds because they consist of metal and nonmetal combinations, while CO_2 is the covalent compound among the options.