Organic Chemistry – Some Basic Principles and Techniques

Chemistry · Class 11

Simulation · Chemistry · Class 11

Counting σ and π bonds

"Counting σ and π bonds" is a free, interactive Class 11 Chemistry simulation for NEET and JEE, built on the NCERT section "Carbon's tetravalence and the shapes of organic molecules" in Organic Chemistry – Some Basic Principles and Techniques. A molecule's skeleton with every carbon's hybridisation coloured; tapping a bond reveals its σ and π orbitals (head-on vs sideways), with running σ/π tallies and % s character. NEET has asked about this idea 3 times in 10 years of papers. JEE Main asked 91 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).

From the lesson Carbon's tetravalence and the shapes of organic molecules in Organic Chemistry – Some Basic Principles and Techniques. Change the values and watch what happens.

Counting σ and π bondsChemistry · Class 11

What it shows

NCERT § "Tetravalence of Carbon: Shapes of Organic Compounds"

A molecule's skeleton with every carbon's hybridisation coloured; tapping a bond reveals its σ and π orbitals (head-on vs sideways), with running σ/π tallies and % s character.

Controls

3 to try

  • Segmentedmolecule CH2=CH–C≡N / CH2=C=CH2 / HC≡C–CH=CH2 / benzene
  • Tapa bond to open its orbitals
  • Toggleshow unhybridised p orbitals

Try this

For CH2=CH–C≡N, enter the counts 6 σ and 3 π; goal checks both.

Common mistake

A triple bond is three σ bonds; C–H bonds forgotten in σ counts.

In NEET

10 years of papers

Asked 3 times in 10 years of NEET.

See the past questions: Hybridization, Organic Chemistry - Some Basic Principles and Techniques (chapter)

In JEE Main

42 shifts analysed

91 questions from Organic Chemistry – Some Basic Principles and Techniques across the 42 JEE Main shifts Lumi has analysed (2017–2026).

See the past questions

The idea behind it

NCERT § "Tetravalence of Carbon: Shapes of Organic Compounds"

  • Carbon is tetravalent and forms covalent bonds using hybrid orbitals: sp³ (tetrahedral, as in CH₄), sp² (trigonal planar, as in C₂H₄) and sp (linear, as in C₂H₂).
  • s character is 25% in sp³, 33% in sp² and 50% in sp; more s character holds electrons closer to the nucleus.
  • An sp-hybridised carbon is therefore more electronegative than sp², which is more electronegative than sp³.
  • More s character also means shorter and stronger bonds formed by that carbon.
  • A π bond forms by sideways overlap of unhybridised p orbitals; the two atoms joined by it and the atoms attached to them must lie in one plane, and rotation about the double bond is restricted.
  • π electrons lie above and below the bond axis and are loosely held, so multiple bonds are reactive centres attacked by electron-seeking reagents.

Questions

5 answers

What does the "Counting σ and π bonds" simulation show?
A molecule's skeleton with every carbon's hybridisation coloured; tapping a bond reveals its σ and π orbitals (head-on vs sideways), with running σ/π tallies and % s character.
What mistake does the "Counting σ and π bonds" simulation fix?
A common mistake it clears up: A triple bond is three σ bonds; C–H bonds forgotten in σ counts.
Has NEET asked about this idea?
Yes. NEET has asked about this idea 3 times in 10 years of papers.
Does JEE Main ask questions from Organic Chemistry – Some Basic Principles and Techniques?
Yes. JEE Main asked 91 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
Is this simulation free?
Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Carbon's tetravalence and the shapes of organic molecules" in Organic Chemistry – Some Basic Principles and Techniques (Class 11 Chemistry).

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