Question

Which of the following is a pseudo halogen?
A.$IF_7$
B.$C{{N}^{-}}$
C.$ICl_2$
D.$I{{3}^{-}}$

Answer 1

Hint:
The halogens are a group in the periodic table consisting of five chemically related elements - fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The group of halogens is the only periodic table group that contains elements in three of the main states of matter at standard temperature and pressure. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts. The middle halogens—chlorine, bromine, and iodine—are often used as disinfectants. The halogens form homonuclear diatomic molecules (not proven for astatine). Due to relatively weak intermolecular forces, chlorine and fluorine form part of the group known as "elemental gases".
The elements become less reactive and have higher melting points as the atomic number increases. The higher melting points are caused by stronger London dispersion forces resulting from more electrons

Complete step by step answer:
Pseudohalogens are also known as halogenoids .A molecule consisting of more than two electronegative atoms which in free state resemble the halogen. The pseudo halogen gives rise to anions which resemble the halide ions in their behaviour .
Eg : $\left( CN \right)_2$ ,$\left( SCN \right)_2$ ,Their ions $C{{N}^{-}}$,$SC{{N}^{-}}$ behaves similar to halide ions.
Hence option B is the correct answer.

Note: INTERHALOGEN COMPOUNDS - When two different halogens react with each other, interhalogen compounds are formed. ...
In general, \[XYn\] where n=1 , 3 , 5 , 7 \[X\] is a halogen atom which is less electronegative and larger in size.
Similarities between halogens and pseudohalogens:
-Volatile in free state
-Isomorphous in their structure
-Both forms intermolecular and complex compounds