There is ammonia gas, #NH_3(g)#, a high-boiling, room temperature gas, that has good solubility in water....
#NH_3(g) stackrel(H_2O)rarrNH_3(aq)#
And this is supplied in the labs as concentrated ammonia or (inaptly named) ammonium hydroxide as AQUEOUS solutions.
Ammonia behaves as a BASE in aqueous solution....
#NH_3(aq) + H_2O(l) rightleftharpoons NH_4^+ + HO^-# #;pK_b=4.71#
You can take bottled ammonia (#"boiling point,"# #-33.3# #""^@C#) and condense it in a dry-ice/ethanol condenser, and use ammonia as a SOLVENT that allows formation of more nucleophilic reagents. Liquid ammonia also undergoes an acid-base equilibrium equivalent to that which occurs in water...
#2NH_3(l)rightleftharpoonsNH_4^+ + NH_2^(-)#
The #NH_2^-# ion, #"the amide ion"#, is the ammonia equivalent of hydroxide ion. #NH_2^-# CANNOT exist in water....
For #NH_4^(+)#, #NH_3#, #NH_2^(-)#, #NH^(2-)#...ALL the electronic geometries are based on a tetrahedron in that there are 4 electron pairs, bonding or non-bonding, around the central nitrogen. Of course the geometry of the molecule might not be tetrahedral......
