How to Determine the Hybridization and Shape of NO3– Ion
The hybridization of NO3 (nitrate ion) is a central concept in JEE Main Chemistry, helping you predict the ion’s molecular shape and bonding. To answer questions such as "What is the state of hybridization of nitrogen in NO3– ion?" you must examine its Lewis structure, electron domains, and resonance. Mastering this topic will also improve your confidence in structural questions for p-block elements and chemical bonding.
Fundamentals: Structure and Valence Electrons of NO3–
The nitrate ion, NO3–, consists of a central nitrogen atom bonded to three oxygen atoms. Nitrogen contributes 5 valence electrons, each oxygen adds 6, and an extra electron accounts for the -1 charge, giving a total of 24 valence electrons. The actual structure is best described using resonance, where double and single bonds delocalize over all the oxygens.
- Nitrogen: 5 valence electrons
- Oxygen: 3 × 6 = 18 valence electrons
- Negative charge: +1 electron
- Total valence electrons: 24
- Lewis structure shows three N–O bonds, one as a double bond in each resonance form
Delocalization makes all N–O bonds equivalent, with partial double bond character. This is vital when considering hybridization in NO3 and when handling similar ions, such as carbonate or sulfate.
Determining the Hybridization of Nitrogen in NO3–
To find the hybridization of NO3 ion’s central atom, count regions of electron density around nitrogen (bonding pairs + lone pairs). For NO3–:
- Draw the best Lewis structure for NO3– and identify the central atom (nitrogen).
- Count all sigma bonds between nitrogen and oxygen: 3 (ignore pi bonds for hybridization).
- Check for lone pairs on nitrogen: In NO3–, nitrogen has 0 lone pairs.
- Steric number = number of sigma bonds + number of lone pairs = 3.
- Steric number 3 indicates sp2 hybridization (as per the sp, sp2, sp3 pattern: 2 → sp, 3 → sp2, 4 → sp3).
Thus, the state of hybridization of nitrogen in NO3– is sp2. All three hybrid orbitals form sigma bonds to oxygen, with the unhybridized p orbital overlapping for resonance (pi bonding).
Molecular Geometry: Shape and Bond Angles
The sp2 hybridization of NO3– leads to a planar triangular arrangement. The geometry is trigonal planar, with three equivalent N–O bonds and bond angles of approximately 120°.
| Parameter | Detail |
|---|---|
| Hybridization type | sp2 |
| Steric number | 3 |
| Bonding pairs (N–O) | 3 |
| Lone pairs on N | 0 |
| Shape | Trigonal planar |
| Ideal bond angle | 120° |
All N–O bonds are the same length due to resonance, and the nitrate ion’s planar geometry is easy to visualize for quick exam solutions.
Hybridization of NO3 vs NO2: Key Differences
Comparing hybridization of NO3 (sp2) with nitrite ion (NO2–) reinforces concepts and prevents typical exam errors. In NO2–, nitrogen has two bonding pairs and one lone pair, giving a steric number of 3 and thus also sp2 hybridization. However, their shapes differ: NO3– is trigonal planar, while NO2– is angular (bent) because of the lone pair on nitrogen.
| Ion | Central Atom Hybridization | Steric Number | Molecular Shape |
|---|---|---|---|
| NO3– | sp2 | 3 | Trigonal planar |
| NO2– | sp2 | 3 | Bent/V-shaped |
This contrast highlights the impact of bonding pairs versus lone pairs on geometry, despite identical hybridization types.
Exam-Ready Strategies and Common Traps
When you see "hybridization of NO3" in JEE Main, remember these tips to avoid common mistakes:
- Count only sigma bonds + lone pairs for hybridization—not pi bonds.
- All three N–O bonds in NO3– are equivalent due to resonance, so don’t assign different hybridizations.
- Don’t confuse shape (“trigonal planar” in NO3–) with arrangement of atoms in similar ions like NO2– (bent).
- Use VSEPR theory fast: steric number 3 → sp2 → planar geometry, no lone pairs = flat shape.
- Practise resonance sketching to see that all atoms are symmetrically bonded in nitrate.
- In calculations or matching questions, highlight final answers (e.g., "sp2 hybridization").
Applying these ideas makes structural and hybridization questions in chemical bonding faster and more accurate for exams.
Application Checklist: Mastering Hybridization of NO3 for JEE Main
- Review Lewis and resonance structures for NO3–, carbonate, and sulfate ions.
- Memorize steric number–hybridization mapping: 2 → sp, 3 → sp2, 4 → sp3.
- Practice with previous JEE Main papers on p-block elements.
- Clarify differences with NO2 hybridization and nitrate vs nitrite ions.
- Link hybridization to geometry with VSEPR theory examples.
- For comprehensive theory, see chemical bonding revision notes.
- Check the resonance effect for stable ion structures.
- Test yourself with chapterwise JEE Chemistry practice for structural concepts.
By following this approach, you will confidently answer questions on the hybridization of NO3 as sp2 and analyze similar ions in seconds. For more help, explore detailed topic guides and solved problems on Vedantu. Remember, conceptual clarity is key to maximizing your Chemistry score.
FAQs on Hybridization of NO3–: Detailed Concept and Explanation
1. What is the hybridization of NO3–?
NO3– (nitrate ion) has sp2 hybridization. This means the nitrogen atom forms three sigma bonds and adopts a trigonal planar geometry with 120° bond angles.
- Hybridization: sp2
- Shape: Trigonal planar
- Bond angles: 120°
- Basis: Nitrogen uses three hybrid orbitals for bonding, with no lone pairs
2. How do you determine the hybridization of the nitrate ion?
To determine the hybridization of NO3–, count the number of sigma bonds and lone pairs on the central nitrogen atom.
- Nitrogen is bonded to three oxygen atoms via sigma bonds
- There are no lone pairs on nitrogen in the Lewis structure
- Number of electron domains (steric number) = 3
- Steric number 3 ⇒ sp2 hybridization
3. Why is NO3– sp2 hybridized?
The NO3– ion is sp2 hybridized because its central atom (nitrogen) has three regions of electron density.
- Nitrogen forms three sigma bonds with oxygen atoms
- There are no lone pairs on nitrogen
- Three electron domains = sp2 hybridization
- This results in a trigonal planar shape
4. What is the Lewis structure and bond order of NO3–?
The Lewis structure of NO3– shows nitrogen single-bonded to two oxygens and double-bonded to one oxygen, with resonance among all three positions.
- There are three equivalent resonance structures
- Each N–O bond is between a single and double bond
- Bond order = Total number of N–O bonds / Total number of equivalent bonds = 4/3 = 1.33
5. How is NO3– different from NO2– in terms of hybridization?
NO3– and NO2– differ in hybridization due to variations in their electron domains:
- NO3– (nitrate ion): sp2 hybridized, trigonal planar geometry, three sigma bonds
- NO2– (nitrite ion): sp2 hybridized as well, but has one lone pair, resulting in a bent shape
- Key difference: NO2– has a lone pair, NO3– does not
6. What hybridization is NO3?
NO3– is sp2 hybridized.
- This hybridization gives the nitrate ion its trigonal planar geometry
- The nitrogen atom forms three sigma bonds
- All bond angles are 120°
7. How to determine hybridization of NO3?
To determine the hybridization of NO3–:
- Draw the Lewis structure of NO3–
- Count the number of sigma bonds (3) to oxygen atoms
- Check for lone pairs on nitrogen (none)
- Steric number = 3 (sigma bonds + lone pairs)
- Steric number 3 ⇒ sp2 hybridization
8. Can NO3– have an sp3 or sp hybridization?
NO3– cannot exhibit sp3 or sp hybridization.
- Number of electron domains on nitrogen = 3
- sp2 hybridization occurs with 3 domains
- sp3 (4 domains) or sp (2 domains) do not match the nitrate ion's structure
9. Is hybridization related to resonance in NO3–?
Yes, hybridization is related to resonance in NO3–.
- Resonance ensures all three N–O bonds are equivalent
- The underlying hybridization of nitrogen remains sp2 across all resonance forms
- Electron delocalization does not change the number of electron domains used for hybridization
10. What does the Lewis structure and geometry of NO3– look like?
The Lewis structure of NO3– displays
- Nitrogen at the center, singly bonded to two oxygen atoms and doubly bonded to one, with negative charge delocalized
- Three equivalent resonance structures
- The geometry is trigonal planar with 120° bond angles
11. How can you use VSEPR theory to predict the geometry of NO3–?
Using VSEPR theory for NO3– involves:
- Identifying three bonding domains on central nitrogen
- No lone pairs present
- Three electron domains → trigonal planar geometry
- Bond angles are approximately 120°
12. Why is the geometry of NO3– described as trigonal planar?
The NO3– ion is described as trigonal planar due to its sp2 hybridization.
- Nitrogen forms three equivalent sigma bonds with no lone pairs
- Electron domains orient themselves at 120° angles for minimal repulsion
- This creates a flat, triangular shape
