Topics
Some Basic Concepts of Chemistry
Introduction to Analytical Chemistry
- Introduction of Analytical Chemistry
- Analysis
- Mathematical Operation and Error Analysis
- Determination of Molecular Formula
- Chemical Reactions and Stoichiometric Calculations
- Limiting Reagent
- Concentration of a Solution
- Use of Graph in Analysis
Basic Analytical Techniques
- Introduction of Some Analytical Techniques
- Purification of Solids
- Crystallisation Method
- Fractional Crystallization
- Simple Distillation Method
- Solvent Extraction
- Chromatography Method
- Chromatography Method > Adsorption Chromatography
- Chromatography Method > Partition Chromatography
Structure of Atom
Chemical Bonding
- Concept of Chemical Bonding
- Kossel-lewis Approach to Chemical Bonding - Octet Rule
- Kossel and Lewis Approach to Chemical Bonding
- Formal Charge
- Limitations of the Octet Rule
- Valence Shell Electron Pair Repulsion (VSEPR) Theory
- Valence Bond Theory (VBT)
- Molecular Orbital Theory
- Parameters of Covalent Bond
- Dipole Moment
- Resonance
Redox Reactions
Modern Periodic Table
- Introduction of Periodic Table
- Structure of the Modern Periodic Table
- Periodic Table and Electronic Configuration
- Blockwise Characteristics of Elements
- Periodic Trends in Elemental Properties
Elements of Group 1 and 2
Elements of Group 13, 14 and 15
- Electronic Configuration of Elements of Groups 13, 14 and 15
- Trends in Atomic and Physical Properties of Elements of Groups 13, 14 and 15
- Chemical Properties of the Elements of the Groups 13,14 and 15
- Carbon: A Versatile Element
- Allotropes of Carbon > Diamond
- Molecular Structures of Some Important Compounds of the Group 13, 14 and 15 Elements
- Chemistry of Notable Compounds of Elements of Groups 13, 14 and 15
States of Matter
- States of Matter
- Intermolecular Forces
- Characteristic Properties of Gases
- Gas Laws
- Ideal Gas Equation
- Kinetic Molecular Theory of Gases
- Deviation from Ideal Behaviour
- Liquefaction of Gases and Critical Constant
- Liquid State
Adsorption and Colloids
- Introduction of Adsorption
- Adsorption
- Types of Adsorption
- Factors Affecting Adsorption of Gases on Solids
- Adsorption Isotherms (Freundlich and Langmuir Adsorption Isotherm)
- Applications of Adsorption
- Catalysis
- Adsorption Theory of Heterogeneous Catalysis
- Colloids
Chemical Equilibrium
- Introduction of Chemical Equilibrium
- Equilibrium in Physical Processes
- Equilibrium in Chemical Processes - Dynamic Equilibrium
- Law of Mass Action and Equilibrium Constant
- Homogeneous and Heterogenous Equilibria
- Characteristics of Equilibrium Constant
- Applications of Equilibrium Constants
- Le Chaterlier's Principle and Factors Altering the Composition of Equilibrium
- Industrial Application
Nuclear Chemistry and Radioactivity
- Introduction: Nuclear Chemistry is a Branch of Physical Chemistry
- Classification of Nuclides
- Nuclear Stability
- Radioactivity
- Radioactive Decays
- Modes of Decay
- Nuclear Reactions
- Applications of Radio Isotopes
Basic Principles of Organic Chemistry
- Organic Chemistry
- Structural Representation of Organic Molecules
- Classification of Organic Compounds
- Nomenclature
- Isomerism
- Theoretical Basis of Organic Reactions
Hydrocarbons
Chemistry in Everyday Life
- Chemistry in Everyday Life
- Basics of Food Chemistry
- Compounds with Medicinal Properties
- Cleansing Agents
Estimated time: 9 minutes
Maharashtra State Board: Class 12
Definition: Oxidation Number
Oxidation number (also called oxidation state) is the charge that an atom of an element appears to have when present in a combined state with other atoms. It is a hypothetical charge assigned by assuming all bonds are ionic — atoms in real molecules like H₂O do not actually carry these charges.
Maharashtra State Board: Class 12
Key Points: Oxidation Number
Rules for Assigning Oxidation Numbers:
| Species | Rule |
|---|---|
| Free elements | Oxidation number = 0 (e.g., Na, O₂, O₃, Hg, S₈, P₄) |
| Monoatomic ions | Oxidation number = charge on the ion (e.g., Mn²⁺ = +2, Cr³⁺ = +3) |
| Fluorine | Always −1 in all compounds |
| Oxygen | Usually −2; Exceptions: −1 in peroxides (H₂O₂), −1/2 in superoxides (KO₂), +2 in oxygen fluoride (OF₂) |
| Hydrogen | Usually +1; Exception: −1 in metal hydrides (e.g., CaH₂, NaH) |
| Halogens (Cl, Br, I) | Usually −1 in binary compounds; can be positive when bonded to a more electronegative element or oxygen |
| Neutral compound | Sum of all oxidation numbers = 0 |
| Polyatomic ion | Sum of all oxidation numbers = charge on the ion |
- Oxidation number of N can be −3 (bonded to less electronegative atoms) or +3 (bonded to more electronegative atoms)
- Oxidation number of halogens is always −1 in metal halides
- In interhalogen compounds, the more electronegative halogen gets the oxidation number of −1
- Oxidation number of metals in amalgams and carbonyls is zero (e.g., Fe in [Fe(CO)₅] = 0)
- In complex ions, the algebraic sum of oxidation numbers of all atoms = net charge on the ion
- Oxidation number can be positive, negative, zero, a whole number, or a fraction
- Oxidation number greater than +6 or less than −4 is unusual — double-check for errors
Stock Notation
Variable oxidation states are indicated using Roman numerals in parentheses after the element symbol:
| Formula | Name | Stock Notation |
|---|---|---|
| Cu₂O | Cuprous oxide | Copper (I) oxide |
| Fe₂O₃ | Ferric oxide | Iron (III) oxide |
| HgCl₂ | Mercuric chloride | Mercury (II) chloride |
| SnCl₂ | Stannous chloride | Tin (II) chloride |
