Question

Which one of the following forms with an excess of $CN^-$ (cyanide) a complex having coordination number two?

• A. $Cu ^{+}$
• B. $Ag ^{+}$
• C. $Ni ^{2+}$
• D. $Fe ^{2+}$

Answer 1

Answer: (B)

$Ag ^{+}$

Answer 2

Among the given metal ions only $Ag ^{+}$forms complex with $CN ^{-}$having co-ordination number $2$ . $Ag ^{+}+2 CN ^{-} \longrightarrow\left[ Ag ( CN )_{2}\right]^{-}$ Coordination number of metals is defined as the number of $\sigma$ bonds by which ligands are attached to the metal atom.