Q.The hybridisation state of nitrogen in trimethylamine is -

In trimethylamine $(\text{CH}_3)_3\text{N}$, nitrogen has three bond pairs and one lone pair → four electron domains → $sp^3$ hybridisation.

Nitrogen in amines is generally sp3 hybridised, using three orbitals to bond to substituents and the fourth to hold the lone pair.

In trimethylamine, (CH3)3N, nitrogen is bonded to three methyl (CH3) groups and carries one lone pair. …

The nitrogen atom in an amine is sp3 hybridised, similar to nitrogen in ammonia, with one hybrid orbital holding the lone pair.

In amines (R-NH2, R2NH, R3N), the nitrogen atom has one lone pair of electrons and forms sigma bonds to the attached carbon/hydrogen atoms. To accommodate 3 bond pairs and 1 lone pair with minimum repulsion, nitrogen adopts sp3 hybridisation, similar to nitrogen in NH3.

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