In the ammonium ion, all four nitrogen to hydrogen bonds are identical even though one was formed as a dative bond because

  • A. the dative bond breaks immediately
  • B. once formed, the origin of the electron pair no longer affects the bond
  • C. nitrogen changes its hybridisation
  • D. one hydrogen leaves the ion

Explanation

A bond is defined by the shared pair between the two nuclei, not by which atom supplied the electrons, so experimentally the four bonds have the same length and strength. The nitrogen is sp3 hybridised and the ion is tetrahedral. This is a favourite examination point because the formation and the final structure are so easily confused.

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