Which of the following compounds is classified as ionic?

• A. NaCl
• B. H_2O
• C. CO_2
• D. C_6H_{12}O_6

Answer: (A)

Verified step by step guidance

1. Understand the difference between ionic and covalent compounds: Ionic compounds are formed by the transfer of electrons between metals and nonmetals, resulting in positive and negative ions held together by electrostatic forces. Covalent compounds involve the sharing of electrons between nonmetals.
2. Identify the elements in each compound and their typical bonding behavior: NaCl consists of sodium (a metal) and chlorine (a nonmetal), which typically form ionic bonds. H_2O, CO_2, and C_6H_{12}O_6 are composed only of nonmetals, which usually form covalent bonds.
3. Recall that ionic compounds generally have high melting points and conduct electricity when molten or dissolved in water, due to the presence of ions.
4. Recognize that NaCl is a classic example of an ionic compound because it is formed from a metal (Na) donating an electron to a nonmetal (Cl), creating Na^+ and Cl^- ions.
5. Conclude that among the given options, NaCl is classified as ionic, while H_2O, CO_2, and C_6H_{12}O_6 are covalent compounds.