17.33 6th edition

[Arshia Ramesh 1G]

How are you able to tell the maximum number of places on the ligand that can bind simultaneously to a single metal center for CO3 2-? Do you have to draw out the lewis structure?

[Mindy Kim 4C]

Yes, drawing out the Lewis structure will help in determining this. If you look at the Lewis structure for CO3 2-, all oxygens have at least two lone pairs (two oxygen atoms have single bonds with the carbon atom and have 3 lone pairs, one oxygen atom has a double bond with the carbon atom and has 2 lone pairs). The molecular geometry of CO3 2- is trigonal planar. Therefore, any one oxygen atom or any two oxygen atoms can coordinate with a metal (monodentate or bidentate). However, CO3 2- cannot be tridentate because it would be difficult for all oxygen atoms to coordinate with the same metal atom due to the trigonal planar shape.