Coordination Compounds Class 12 NCERT Solutions form a crucial part of inorganic chemistry in the CBSE syllabus. This chapter helps students understand how complex compounds form, their structures, and how they behave chemically. The NCERT solutions simplify each exercise, making it easier to grasp the logic behind bonding, nomenclature, and coordination numbers.
In Class 12 Chemistry, coordination compounds are not only important for board exams but also for Competitive Exams like JEE Main, JEE Advanced, and NEET. Questions often revolve around the types of ligands, oxidation states, and isomerism. By solving these NCERT problems, students build confidence in applying theoretical knowledge to numerical and conceptual problems.
This page provides a complete explanation of the chapter, including structured tables, equations, and solved exercises. You will also find conceptual insights, short tricks, and FAQs that will help strengthen your understanding of coordination chemistry.
Coordination Compounds Class 12 NCERT Solutions
- Overview of Coordination Compounds
- Nomenclature and Oxidation States
- Types of Isomerism
- Bonding in Coordination Compounds
- FAQs
Overview of Coordination Compounds
Definition and Key Terms
| Term | Definition | Example |
|---|---|---|
| Coordination Compound | Compound containing a central metal atom bonded to ligands through coordinate bonds | [Cu(NH3)4]SO4 |
| Ligand | Ion or molecule that donates a lone pair to the metal center | NH3, Cl–, CN– |
| Coordination Number | Number of ligands attached to the central metal | 6 in [Co(NH3)6]Cl3 |
| Central Metal Atom | Metal ion that forms coordinate bonds with ligands | Co3+ in [Co(NH3)6]Cl3 |
Coordination compounds play an essential role in analytical chemistry and biochemistry. The coordination number depends on the size and charge of the metal ion and the nature of the ligands. Complexes such as [Fe(CN)6]3− are found in electrochemistry and transition metal reactions. Understanding how ligands interact with the metal center is the first step in mastering the topic.
In biological systems, coordination compounds exist in hemoglobin (Fe complex) and chlorophyll (Mg complex). Therefore, studying their chemistry also helps explain many natural processes like oxygen transport and photosynthesis.
Nomenclature and Oxidation States
Rules and Examples
| Rule | Description | Example |
|---|---|---|
| 1 | Name the cation before the anion | [Co(NH3)6]Cl3 → Hexaamminecobalt(III) chloride |
| 2 | Ligands are named alphabetically before the metal | [Cr(H2O)4Cl2]Cl → Tetraaquadichlorochromium(III) chloride |
| 3 | Oxidation state of the metal is written in Roman numerals | [Fe(CN)6]4− → Hexacyanoferrate(II) |
| 4 | Use prefixes like di-, tri-, tetra- for identical ligands | [Ni(CO)4] → Tetracarbonylnickel(0) |
Nomenclature in coordination chemistry follows a specific order that ensures clarity. The central atom’s oxidation state is calculated by considering the charges of all ligands and the overall charge of the complex. For instance, in \([Co(NH_3)_6]^{3+}\), cobalt has an oxidation state of +3 because each ammonia molecule is neutral.
Students must memorize the common ligand names like “ammine” for NH3, “aqua” for H2O, and “chloro” for Cl–. Correct naming is often tested in board exams, so consistent practice using NCERT exercises is essential.
Types of Isomerism in Coordination Compounds
Structural and Stereoisomerism
| Type | Nature | Example |
|---|---|---|
| Ionization Isomerism | Different ions are formed in solution | [Co(NH3)5Br]SO4 & [Co(NH3)5SO4]Br |
| Hydrate Isomerism | Water molecule acts as a ligand or is outside the coordination sphere | [Cr(H2O)6]Cl3, [Cr(H2O)5Cl]Cl2·H2O |
| Linkage Isomerism | Ligands bond through different donor atoms | [Co(NH3)5(NO2)]Cl2 and [Co(NH3)5(ONO)]Cl2 |
| Geometrical Isomerism | Different spatial arrangement of ligands | cis-[Pt(NH3)2Cl2] and trans-[Pt(NH3)2Cl2] |
| Optical Isomerism | Non-superimposable mirror images | [Co(en)3]3+ → d- and l-forms |
Isomerism explains how compounds with the same chemical formula can have different properties. Geometrical isomers show differences in melting point and dipole moment, while optical isomers rotate plane-polarized light in opposite directions. These properties are widely applied in drug design and coordination chemistry.
Understanding isomerism is critical for solving board exam questions that require identifying and naming various isomers. Students should visualize 3D arrangements and practice drawing cis/trans and enantiomeric structures.
Bonding in Coordination Compounds
Valence Bond Theory and Crystal Field Theory
| Theory | Key Concept | Example |
|---|---|---|
| Valence Bond Theory (VBT) | Hybridization explains geometry and magnetic behavior | [Ni(CN)4]2− → dsp2 hybridization (square planar) |
| Crystal Field Theory (CFT) | Electrostatic interactions between ligands and metal orbitals | [Fe(H2O)6]2+ shows high-spin configuration |
| Crystal Field Splitting | d-orbitals split into t2g and eg levels | ( Delta_0 ) represents the crystal field splitting energy |
Bonding theories explain the structure and magnetism of coordination compounds. According to VBT, the metal-ligand bond is formed by overlap between empty metal orbitals and ligand lone pairs. For example, \([Co(NH_3)_6]^{3+}\) shows d2sp3 hybridization, leading to an octahedral shape.
Crystal Field Theory (CFT) provides a quantitative approach, explaining color, stability, and magnetic behavior. The energy difference between orbitals (\(Delta_0\)) determines whether a compound is high-spin or low-spin. These principles are vital for understanding transition metal chemistry in both inorganic and bioinorganic systems.