Which of the following statements correctly describes the Lewis dot structure of the arsenate ion, AsO_4^{3-}?

• A. Arsenic is surrounded by four oxygen atoms, with one double bond and three single bonds, and the ion carries a -3 charge.
• B. Arsenic is bonded to three oxygen atoms with double bonds and one oxygen atom with a single bond, and the ion carries a -3 charge.
• C. Arsenic is surrounded by four oxygen atoms, each with a single bond, and the ion carries a -3 charge.
• D. Arsenic is surrounded by four oxygen atoms, each with a double bond, and the ion carries a -3 charge.

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons available for the arsenate ion, AsO_4^{3-}. Arsenic (As) has 5 valence electrons, each oxygen (O) has 6 valence electrons, and the ion has an extra 3 electrons due to the -3 charge. Calculate the total valence electrons by summing these contributions.
2. Step 2: Draw a skeletal structure with arsenic as the central atom bonded to four oxygen atoms. Connect arsenic to each oxygen with single bonds initially.
3. Step 3: Distribute the remaining valence electrons to satisfy the octet rule for the oxygen atoms first, placing lone pairs on oxygens to complete their octets.
4. Step 4: Check the formal charges on each atom. To minimize formal charges, convert one of the As–O single bonds into a double bond by sharing a lone pair from an oxygen with arsenic. This helps reduce the overall formal charge on the ion.
5. Step 5: Confirm that the final Lewis structure has arsenic surrounded by four oxygen atoms, with one double bond and three single bonds, and that the overall charge of the ion is -3, consistent with the given charge.