Welcome to ChemZipper !!!: What are Pseudohalides ? and What is similarity with halides?

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What are Pseudohalides ? and What is similarity with halides?

The ions consisting of two or more electronegative atoms of which at least one is
nitrogen, that have properties similar to those of halide ions. These ions are called pseudohalide ions, Pseudohalide ions are univalent and these form salts resembling halide salts. The pseudohalide ions are :
Cyanide ions (CN-) 
Isocyanide ion (NC-)
Cyanate ion (OCN-)
Fulminate ion (ONC-)
Thiocyanate ions(SCN-)
Isothiocyanate ion (NCS-)
Selenocyanate ion (SeCN-)
Tellurocyanate ion (TeCN-)
Azide ion (N3-) :
Azido carbon disulphide ion (SCSN-_3)

The best known pseudohalide is CN-.This resembles Cl- , Br- and I- in the following respects:
(i) It forms an acid, HCN.
(ii) It can be oxidised to (CN)2 molecule.
(iii) It forms insoluble salts with Ag+, Pb2+ and Hg22+
(iv) It forms large number of complexes similar to halide complexes, e.g. [Cu (CN)4]2- and [CuCl4]2, [Co(CN)6]3- and [CoCl6]3-
(v) Inter-pseudohalogen compounds ClCN, BrCN and ICN can be formed.
(vi) AgCN is insoluble in water but soluble in ammonia likeAgCl.

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