CBSE Class 12 Chemistry - Coordination Compounds Chapter Notes. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.
2. Coordination entity: A coordination entity constitutes a central metal atom or ion bonded to a fixed number of ions or molecules. Example: in K4[Fe(CN)6], [Fe(CN)6]4- represents coordination entity.
3. Central atom or ion: In a coordination entity, the atom/ion to which a fixed number of ions/groups are bound in a definite geometrical arrangement around it, is called the central atom or ion. E.g.: in K4[Fe(CN)6], Fe²+ is the central metal ion.
4. Ligands: A molecule, ion or group that is bonded to the metal atom or ion in a complex or coordination compound by a coordinate bond is called ligand. It may be neutral, positively or negatively charged. Example: H2O, CN-, NO+ etc.
5. Donor atom: An atom of the ligand attached directly to the metal is called the donor atom. For example: in the complex K4[Fe(CN)6], carbon is a donor atom.
6. Coordination number: The coordination number (CN) of a metal ion in a complex can be defined as the number of ligand donor atoms to which the metal is directly bonded. For example: in the complex K4[Fe(CN)6], the coordination number of Fe is 6.
7. Coordination sphere: The central atom/ion and the ligands attached to it are enclosed in square bracket and is collectively termed as the coordination sphere. For example: in the complex K4[Fe(CN)6], [Fe(CN)6]4- is the coordination sphere.
8. Counter ions: The ions present outside the coordination sphere are called counter ions. For example: in the complex K4[Fe(CN)6], K+ is the counter ion.
9. Coordination polyhedron: The spatial arrangement of the ligand atoms which are directly attached to the central atom/ ion defines a coordination polyhedron about the central atom. The most common coordination polyhedra are octahedral, square planar and tetrahedral. For example: [PtCl4]2- is square planar, Ni(CO)4 is tetrahedral while [Cu(NH3)6]3+ is octahedral.
10. Charge on the complex ion: The charge on the complex ion is equal to the algebraic sum of the charges on all the ligands coordinated to the central metal ion.
11. Denticity: The number of ligating (linking) atoms present in ligand is called denticity.
12. Unidentate ligands: The ligands whose only one donor atom is bonded to metal atom are called unidentate ligands. Example: H2O, NH3, CO, CN-
13. Didentate ligands: The ligands which contain two donor atoms or ions through which they are bonded to the metal ion. For example: ethylene diamine (H2NCH2CH2NH2) has two nitrogen atoms, oxalate ion has two oxygen atoms which can bind with the metal atom. | COO- - COO-
14. Polydentate ligand: When several donor atoms are present in a single ligand, the ligand is called polydentate ligand. For example: in
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