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Sunday, June 14, 2020

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 ionsPseudohalide 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.

Related Questions:

Why halogens are insoluble in water ?
Is F2 bond is stronger than Br2 ?
Which is best known pseudohalide ?
Iodine forms I3- but F2 does not form F3- ions. Why?
Number of lone pair present at central atom of I3- ion and also give hybridisation and shape of ion?
How many maximum atoms of IF7 are present in the same plane ?
What are the Pseudohalogens or halogenoids?
What are Pseudohalides ? and What is similarity with halides?
Although electron affinity of chlorine is higher than fluorine, yet fluorine act as better oxidizing agent than chlorine? Explain.
Although electron affinity of chlorine is higher than fluorine, yet fluorine act as better oxidizing agent than chlorine? Explain.
Why chlorine trifluoride (ClF3) exists but fluorine trichloride (FCl3) does not?
Why Chlorine (Cl2) bleaches a substance permanently but sulphuredioxide (SO2) does it temporarily?
What is the correct order of electronegativity of Cl atoms in HClO, HClO2, HClO3 and HClO4 ?
How does the thermal stability of oxy acids of chlorine increase with an increase in the oxidation state of chlorine atom ?
Which of the following is a strongest acid among oxy acids of chlorine and why? "HClO, HClO2, HClO3, HClO4"
Which will have very fast tendency to dimerized ClO2 or NO and why?
Which of the following is a strongest acid among oxy acids of chlorine and why? "HClO, HClO2, HClO3, HClO4"

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