Final answer:
From the list of compounds, NaCl is an ionic compound as it consists of a metal cation (Na+) and a non-metal anion (Cl-). The other compounds (HCl, CO₂, CH₄) are covalent, as they involve sharing of electrons between non-metal atoms.
Step-by-step explanation:
The question asks which of the given compounds are ionic. From the options A. HCl, B.CO₂, C. NaCl, and D.CH₄, the ionic compound is C. NaCl. An ionic bond is typically formed between a metal and a non-metal, where electrons are transferred from the metal to the non-metal, resulting in the formation of positively charged metal cations and negatively charged non-metal anions. NaCl (Sodium chloride) consists of Na+ (a metal cation) and Cl- (a non-metal anion), making it an ionic compound. HCl (Hydrogen chloride), B.CO₂ (Carbon dioxide), and D.CH₄ (Methane) are covalent compounds, as they consist of non-metals and the atoms share electrons rather than transferring them.