Syllabus for UPSC Chemistry Optional Subject Exam:

I. Physical Chemistry

1. Atomic Structure and Chemical Bonding
- Atomic structure: Quantum theory, wave-particle duality, wave function, orbitals, quantum numbers, electronic configuration, periodic table.
- Chemical bonding: Ionic, covalent, and coordinate bonds, VSEPR theory, hybridization, molecular orbital theory, hydrogen bonding.

2. Thermodynamics and Chemical Equilibrium
- Laws of thermodynamics, enthalpy, entropy, free energy, spontaneity, equilibrium constant.
- Chemical equilibrium: Le Chatelier's principle, factors affecting equilibrium, ionic equilibrium in solution, solubility product, pH and pOH.

3. Solid State and Solutions
- Solid state: Crystal lattice, unit cell, Bragg's equation, imperfections in solids, electrical and magnetic properties of solids.
- Solutions: Types of solutions, colligative properties, Raoult's law, ideal and non-ideal solutions, colloids and suspensions.

4. Electrochemistry
- Conductance, electrolysis, Faraday's laws, galvanic cells, Nernst equation, corrosion, batteries.

II. Inorganic Chemistry

1. Periodic Table and Chemical Bonding
- Periodic properties: Trends in atomic and ionic radii, ionization energy, electron affinity, electronegativity, periodicity in properties.
- Coordination compounds: Nomenclature, isomerism, bonding theories (VB and crystal field theory), magnetic properties, colored compounds.

2. s, p, and d Block Elements
- Group 1 and 2 elements: General characteristics, compounds, and reactions.
- Group 13 to 18 elements: General characteristics, compounds, and reactions.
- Transition elements: Electronic configurations, oxidation states, coordination compounds, catalysis, magnetic properties.

III. Organic Chemistry

1. Organic Reaction Mechanisms
- Electronic effects: Inductive, electromeric, resonance, and hyperconjugation effects.
- Reaction intermediates: Carbocations, carbanions, free radicals, nucleophiles, electrophiles.
- Substitution, elimination, and addition reactions: SN1, SN2, E1, E2, Markovnikov's rule, anti-Markovnikov's rule.

2. Organic Compounds and their Synthesis
- Alkanes, alkenes, and alkynes: Nomenclature, isomerism, reactions.
- Aromatic compounds: Structure, reactions, electrophilic aromatic substitution.
- Organic compounds with functional groups: Alcohols, ethers, carbonyl compounds, carboxylic acids, amines.

Conclusion:

The UPSC Chemistry optional subject exam covers a wide range of topics in physical, inorganic, and organic chemistry. The syllabus includes atomic structure, chemical bonding, thermodynamics, equilibrium, solid state, solutions, electrochemistry, periodic table, chemical bonding, s, p, and d block elements, organic reaction mechanisms, and organic compounds and their synthesis. It is important for candidates to have a strong understanding of these topics in order to perform well in the exam.