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......
