Draw all resonance structures for the nitryl fluoride molecule, NO2F. Explicitly draw all H atoms. Include all valence lone pairs in your answer. Do not include overall ion charges or formal charges in your drawing. Do not draw double bonds to oxygen unless they are needed for the central atom to obey the octet rule. Draw one structure per sketcher. Add additional sketchers using the drop-down menu. Separate resonance structures using the symbol from the drop-down menu. ChemDoodle?
The Correct Answer and Explanation is:
To determine the resonance structures for nitryl fluoride (NO₂F), we must follow a systematic approach based on the rules of Lewis structures and the specific constraints provided in the problem.
- Count Total Valence Electrons:
- Nitrogen (N) is in Group 15 and has 5 valence electrons.
- Oxygen (O) is in Group 16 and has 6 valence electrons. Since there are two oxygen atoms, they contribute 2 × 6 = 12 electrons.
- Fluorine (F) is in Group 17 and has 7 valence electrons.
- Total valence electrons = 5 (N) + 12 (O₂) + 7 (F) = 24 electrons.
- Determine the Central Atom and Skeletal Structure:
- Nitrogen is the least electronegative atom (excluding hydrogen), so it is the central atom. The two oxygen atoms and the fluorine atom are bonded to the central nitrogen.
- Draw Single Bonds and Distribute Remaining Electrons:
- Start by drawing single bonds from the central nitrogen to each of the three terminal atoms (N-O, N-O, N-F). This uses 3 bonds × 2 electrons/bond = 6 electrons.
- We have 24 – 6 = 18 electrons remaining to be distributed as lone pairs.
- Place lone pairs on the terminal atoms to satisfy their octets. Fluorine and each oxygen atom need 6 more electrons (3 lone pairs). This uses all 18 remaining electrons (3 atoms × 6 electrons/atom).
- At this stage, fluorine and both oxygen atoms have a full octet. However, the central nitrogen atom only has three single bonds, totaling 6 electrons, which is an incomplete octet.
- Form Multiple Bonds to Satisfy the Central Atom’s Octet:
- To give the central nitrogen atom a full octet, we must form a double bond by moving a lone pair from one of the terminal atoms to form a bond with nitrogen.
- The double bond will come from one of the oxygen atoms rather than the fluorine atom. This is because fluorine is the most electronegative element and is highly reluctant to form multiple bonds, which would result in an unfavorable positive formal charge.
- Moving a lone pair from one oxygen atom creates an N=O double bond. The central nitrogen now has one double bond and two single bonds, giving it a complete octet (4 bonds × 2 electrons = 8 electrons). The double-bonded oxygen now has two lone pairs, and the single-bonded oxygen retains its three lone pairs.
- Identify Resonance Structures:
- Since there are two equivalent oxygen atoms, the double bond can be formed with either one. This gives rise to two distinct but equivalent resonance structures.
- Structure 1: One oxygen has a double bond to nitrogen (with 2 lone pairs), while the other oxygen has a single bond (with 3 lone pairs).
- Structure 2: The roles of the oxygen atoms are swapped. The second oxygen now has the double bond, and the first has the single bond.
The final answer consists of these two resonance structures, separated by a resonance arrow (↔). All lone pairs are explicitly drawn, and no formal charges are included, as per the instructions.
Final Answer Drawing:
The correct solution consists of two structures separated by a resonance arrow:
- First Structure: A central nitrogen atom is single-bonded to a fluorine atom and one oxygen atom, and double-bonded to the second oxygen atom. The fluorine atom has three lone pairs. The single-bonded oxygen atom has three lone pairs. The double-bonded oxygen atom has two lone pairs. The central nitrogen has no lone pairs.
- Resonance Arrow: ↔
- Second Structure: A central nitrogen atom is single-bonded to a fluorine atom and the second oxygen atom, and double-bonded to the first oxygen atom. The fluorine atom has three lone pairs. The single-bonded oxygen atom has three lone pairs. The double-bonded oxygen atom has two lone pairs. The central nitrogen has no lone pairs.
