Which of the following best describes the correct Lewis dot structure for the diazomethane molecule, CH2N2?

• A. The central carbon is double-bonded to one nitrogen, single-bonded to the other nitrogen, and single-bonded to both hydrogens; the terminal nitrogen has a negative formal charge, and the central nitrogen has a positive formal charge.
• B. The central carbon is single-bonded to both nitrogens and both hydrogens, with each nitrogen having a lone pair.
• C. The central carbon is single-bonded to both nitrogens and double-bonded to both hydrogens.
• D. The central carbon is triple-bonded to one nitrogen, single-bonded to the other nitrogen, and single-bonded to both hydrogens.

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons in the diazomethane (CH2N2) molecule. Carbon has 4 valence electrons, each hydrogen has 1, and each nitrogen has 5. Sum these to find the total electrons available for bonding and lone pairs.
2. Step 2: Identify the central atom, which is carbon in this case, because it can form four bonds and is less electronegative than nitrogen. Arrange the atoms with carbon in the center, hydrogens bonded to carbon, and nitrogens bonded to carbon.
3. Step 3: Begin by connecting the atoms with single bonds: carbon bonded to two hydrogens and two nitrogens. This uses 8 electrons (4 bonds × 2 electrons each).
4. Step 4: Distribute the remaining electrons to satisfy the octet rule for the nitrogens and carbon. Consider possible multiple bonds (double or triple bonds) between carbon and nitrogens to complete octets and minimize formal charges.
5. Step 5: Calculate formal charges for each atom using the formula \(\text{Formal charge} = \text{Valence electrons} - (\text{Nonbonding electrons} + \frac{1}{2} \times \text{Bonding electrons})\). Choose the structure where formal charges are minimized and placed on atoms according to electronegativity (negative charge on more electronegative atom). This leads to the structure where carbon is double-bonded to one nitrogen, single-bonded to the other nitrogen and hydrogens, with the terminal nitrogen carrying a negative formal charge and the central nitrogen a positive formal charge.