In which of the following ions does carbon have a formal charge?

• A. CH_4
• B. C_2H_6
• C. CO_2
• D. CO_3^{2-}

Answer: (D)

Verified step by step guidance

1. Recall that the formal charge of an atom in a molecule or ion is calculated using the formula: \(\text{Formal Charge} = \text{Valence Electrons} - \text{Nonbonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons}\).
2. Identify the valence electrons for carbon, which is 4, since carbon is in group 14 of the periodic table.
3. Examine each species given: CH\(_4\), C\(_2\)H\(_6\), CO\(_2\), and CO\(_3^{2-}\), and draw their Lewis structures to count bonding and nonbonding electrons around carbon.
4. Calculate the formal charge on carbon in each species by applying the formula to the Lewis structures, paying special attention to CO\(_3^{2-}\), where resonance and extra electrons due to the charge may affect the formal charge on carbon.
5. Determine which species has a carbon atom with a formal charge different from zero; this will be the ion where carbon carries a formal charge.