Class 12 Chemistry - ISC
Coordination Compounds
Coordination Compounds is a crucial chapter in Class 12 ISC Chemistry that explores complex salts where a central metal atom or ion is bonded to a fixed number of molecules or ions called ligands. You will learn about Werner's theory, the IUPAC nomenclature of coordination entities, isomerism in complexes, and bonding theories like Valence Bond Theory (VBT) and Crystal Field Theory (CFT). This chapter holds significant weightage in board exams, frequently featuring direct numerical questions on oxidation states, magnetic moments, hybridisation, and IUPAC naming.
Start Learning FreeKey Concepts
Ligands and Coordination Number
Ligands are neutral molecules or anions that donate a pair of electrons to the central metal atom. The coordination number is the total number of coordinate bonds formed by ligands with the central metal ion.
Werner's Coordination Theory
Proposed that metals exhibit two types of valencies: primary valency (ionisable, oxidation state) and secondary valency (non-ionisable, coordination number, directed in space).
IUPAC Nomenclature
A systematic set of rules used to name coordination compounds by listing ligands alphabetically followed by the metal name, its oxidation state in roman numerals, and the counter-ion.
Valence Bond Theory (VBT)
Explains the formation of complexes based on hybridisation of metal orbitals (e.g., d2sp3 or sp3d2) which dictates the geometry and magnetic properties of the complex.
Crystal Field Theory (CFT)
An electrostatic model that assumes ligands are point charges causing the splitting of degenerate d-orbitals of the central metal into t2g and eg sets, explaining color and magnetic behavior.
Important Formulas
Board Exam Info
In the ISC Class 12 Chemistry examination, this chapter typically carries around 4 to 6 marks. Common question types include writing IUPAC names of given coordination compounds, determining the hybridisation and magnetic moment using VBT or CFT, identifying types of isomerism, and drawing geometrical or optical isomers.
Frequently Asked Questions
How do I determine the oxidation state of the central metal atom?
Assign 'x' to the central metal, add the charges of all ligands, set the sum equal to the overall charge on the coordination sphere, and solve for x.
What is the difference between inner-orbital and outer-orbital complexes?
Inner-orbital complexes use (n-1)d orbitals for hybridisation and are generally low-spin, whereas outer-orbital complexes use nd orbitals and are high-spin.
Why are coordination compounds colored?
Color arises due to d-d electronic transitions, where an electron absorbs a specific wavelength of visible light to jump from one set of d-orbitals to another splitted set.
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