Paper 1 Q16 — Not every carbon is sp³

Bonding — hybridisation and shape follow the number of electron regions

What the examiners said

“Option D, the most common incorrect choice, could be derived if sp³ hybridisation is assumed to be present in all carbon atoms of the three species.”

Try the question (reconstruction)

What is the hybridisation of the carbon atom in carbon dioxide, O=C=O?

Examiner report: “The common error assumed every carbon atom was sp³ hybridised.”

Explore — count regions, get the shape

Pick a molecule. Count the σ-bonding regions and lone pairs on the central atom — that number sets the hybridisation and geometry. Multiple bonds count as one region.

Central atom in: CO2

Regions = σ-bonds + lone pairs. 2 → sp, 3 → sp², 4 → sp³. Double/triple bonds count once.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H2 Chemistry 9729 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org