The coordination number of central metal atom in a complex is determined by
- (A)the number of ligands around a metal ion bonded by sigma bonds✓ Correct
- (B)the number of only anionic ligands bonded to the metal ion
- (C)the number of ligands around a metal ion bonded by sigma and pi- bonds both
- (D)the number of ligands around a metal ion bonded by pi-bonds
Answer: (A)
Solution
The coordination number counts the ligand donor atoms joined to the central metal through sigma bonds, the primary coordinate bonds formed as ligand lone pairs enter the metal's empty orbitals. Both neutral and anionic ligands count, and any pi back-bonding only adds stability without altering the tally. So it is the number of ligands attached by sigma bonds that fixes the coordination number.
JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option