Which of the following statements is correct regarding writing formulas for ionic compounds?

• A. The total positive charge must equal the total negative charge in the compound.
• B. Parentheses are never used in ionic compound formulas, even for polyatomic ions.
• C. The cation is always written after the anion in the formula.
• D. Subscripts are used to indicate the number of ions, but they can be omitted if the ratio is not 1:1.

Answer: (A)

Verified step by step guidance

1. Understand that ionic compounds are formed by the combination of cations (positively charged ions) and anions (negatively charged ions). The key principle is that the overall compound must be electrically neutral.
2. Recognize that the total positive charge contributed by the cations must balance the total negative charge contributed by the anions. This means the sum of the charges in the formula must equal zero.
3. Know that parentheses are used in ionic formulas when there is more than one polyatomic ion present to clearly indicate the number of those ions. Therefore, parentheses can be used in ionic formulas.
4. Remember that the convention for writing ionic formulas is to write the cation first, followed by the anion. This order reflects the positive ion first, then the negative ion.
5. Subscripts in ionic formulas indicate the number of each ion needed to balance the charges. Subscripts should never be omitted, even if the ratio is 1:1, because the formula must explicitly show the ratio of ions.