Dr E. Ramanathan PhD

Level: Class 11, 12, NEET, JEE Chemistry Students

Video

Notes

1. Orbital Basics

• s-orbital: 1 box → max 2 electrons
• p-orbital: 3 boxes → max 6 electrons (px, py, pz)
• d-orbital: 5 boxes → max 10 electrons (dxy, dyz, dxz, dx²−y², dz²)
• f-orbital: 7 boxes → max 14 electrons

---

2. Hybridization Concept

• Orbitals of different energy levels (s, p, d) reorganize during bond formation to attain orbital degeneracy (same energy).
• Common hybridizations:
  • sp³: 1 s + 3 p (tetrahedral, e.g., CH₄)
  • sp²: 1 s + 2 p (trigonal planar, e.g., ethene)
  • sp: 1 s + 1 p (linear, e.g., ethyne)
  • sp³d, sp³d², d²sp³: involve d-orbitals in coordination complexes

---

3. Example: Methane (CH₄)

• Ground state of carbon: 1s² 2s² 2p²
• Excited state: 2s¹ 2p³ (electrons rearranged to form 4 unpaired electrons)
• Resulting hybridization: sp³
• Geometry: Tetrahedral, bond angle ~109°28′

---

4. Example: Ethene (C₂H₄)

• Each carbon is sp² hybridized
• Structure: Trigonal planar
• Bonding:
  • 5 σ bonds: 4 C–H + 1 C–C (σ)
  • 1 π bond: C–C (π)

---

5. Bond Types

• σ (sigma) bond: Axial/linear overlap (stronger)
• π (pi) bond: Sideways overlap (weaker)
  • Rotation around π bonds can break them, while σ bonds remain intact

---

6. Example: Ethyne (C₂H₂)

• Each carbon is sp hybridized
• Structure: Linear
• Bonding: 1 σ + 2 π between C≡C

---

7. Practice Questions & Answers (with Hybridization)

A. Identify hybridization:

Compound	Carbon Hybridization
CH₂=C=O	C1: sp², C2: sp
CH₂=CH–C≡N	C1: sp², C2: sp², C3: sp
CH₃–CH=CH₂	C1: sp³, C2: sp², C3: sp²
(CH₃)₂C=O	CH₃: sp³, central C: sp²
Benzene (C₆H₆)	All C atoms: sp²

---

B. Count σ and π bonds:

Compound	σ Bonds	π Bonds
Benzene (C₆H₆)	12	3
C₆H₁₂ (cyclo/alkene)	18/17	0/1
CH₂Cl₂	4	0
CH₂=C=CH₂	6	2
CH₃NO₂	5	1
HCONHCH₃	8	1

---

8. Structural Insights

• Nitromethane (CH₃NO₂):
  • Coordinate bond between N and O
  • Contains 5 σ bonds + 1 π bond
• N-Methylmethanamide (HCONHCH₃):
  • Amide bond: CONH
  • Contains 8 σ bonds + 1 π bond

---

Worksheets

1. Word Search Game
2. Cross Word Puzzle
3. Online Video Quiz
4. Short Anwer Questions

Short Answer Questions Based on the Hybridization

1. What is the maximum number of electrons an s-orbital can accommodate?
2. Name the three types of p orbitals.
3. How many electrons can be accommodated in a d-orbital?
4. What is the purpose of hybridization in atomic orbitals?
5. Which orbitals combine to form sp³ hybridization?
6. What is the hybridization and geometry of methane (CH₄)?
7. How many sigma bonds are present in ethene (C₂H₄)?
8. What type of overlap forms a sigma bond?
9. Why is a sigma bond stronger than a pi bond?
10. What is the hybridization of each carbon in ethyne (C₂H₂)?
11. Which type of orbital overlap leads to pi bond formation?
12. What hybridization does each carbon atom have in benzene (C₆H₆)?
13. How many pi bonds are present in benzene?
14. What is the total number of sigma and pi bonds in CH₂=CH–CN?
15. What type of bond is formed between nitrogen and oxygen in nitromethane (CH₃NO₂)?

Scan QRCODE for Key