How is #NH_3 # acting in the reaction #H^++:NH_3 ->[H:NH_3]^+#according to the Lewis definition?

1 Answer
MeneerNask
Jan 4, 2015

#NH_3# is acting as an electron donor, so by definition it is a Lewis base.

The lone pair of elctrons from the #N#-atom is (mainly) donated to, are shared with, the proton (#H^+#), after which all four #H#'s fill up a nice tetrahedron around the #N#.

The representation of #[H:NH_3]^+# is not really correct, as all #H#-atoms are completely equal, and the electron deficit (the overall +) is shared around the whole #[NH_4]^+# ammonium -ion.

If the ammonium-ion is dissociated (e.g. in hot alkalic surroundings), there is no telling which of the four #H#'s will leave.

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