Question:

Among the following, which species represents a pseudohalide?

Updated On: Jun 10, 2024
  • $CN^{-}$
  • CaO
  • $I_2$
  • $K_2KhI_4$
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The Correct Option is A

Solution and Explanation

Pseudohalides are 'fake halides'. Their chemistry involves resemblence with true halides $\left( F ^{-}, Cl ^{-}, Br ^{-}, I ^{-}\right) \cdot CN ^{\ominus}$ is a pseudohalide. It has
similar properties to those of halogens. Pseudohalide is any uni-negative species composed of two or more atoms, which in the free state shows certain characteristics of the halogens,
e.g. these combine with hydrogen to form an acid and with silver to form a salt insoluble in water.
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Concepts Used:

Group 17 Elements

Halogens are the group 17 elements of the periodic table. The term ‘halogen’ means ‘salt-producing’, hence the name halogens as they possess the tendency to form salts after reacting to metals. It generally has five elements:

  • Fluorine (F)
  • Chlorine (Cl)
  • Bromine (Br)
  • Iodine (I)
  • Astatine (At)

These are all naturally occurring halogens but Tennessine (Ts) is an artificially created halogen.

Halogens:

Halogens are highly reactive elements and are highly electronegative. They have a high tendency to react with metals to form salts. They are also known as Group 17 elements. They have 7 electrons in their outer shell with a configuration of (ns2 np5). Fluorine being the first halogen in group 17, is highly reactive. Astatine is a halogen because of its resemblance with iodine despite it being radioactive.

Electronic Configuration:

The general electronic configuration for group 17 elements is ns2np5. This configuration clearly shows that they have 7 electrons in their valence shell. They require one more electron to complete their octet and achieve noble gas configuration.