Chemistry Formulas: Complete List of Chemical Compound Formulas

A chemical formula is a symbolic representation of a compound's composition. It shows which elements are present and how many atoms of each element exist in one molecule. For example, H₂O tells you that water has two hydrogen atoms and one oxygen atom. Chemistry formulas come in three types: molecular, empirical, and structural, each used for different purposes in lab work, equations, and examinations.

Chemistry formulas are the language of every reaction, calculation, and board exam question. Without knowing a compound's formula, you cannot write a balanced equation, find molar mass, or identify a reaction type. This page covers all important chemistry formulas for 2026 CBSE exams and NEET, from basic compound tables to class-wise lists for Class 10, 11, and 12. Writing rules, balancing steps, a NEET-focused section, and a 260+ chemical formula list are all included. 

Key Takeaways

Importance of Chemical Formulas

Chemistry formulas are the foundation of every topic in the subject. Every board exam question on reactions, equations, and compounds depends on reading and writing them correctly.

• Chemical formulas show the exact composition of a compound — which elements are present and in what ratio
• They represent the ratios in which elements combine to form a compound
• A formula is needed to write and balance any chemical equation
• Formulas represent ions, free radicals, and other chemical species beyond simple molecules

Types of Chemical Formulas: Molecular, Empirical and Structural

The word "chemical formula" usually refers to the molecular formula, but compounds can be represented in three different ways. Understanding the difference is a direct exam question in Class 9, 10, and 11.

Molecular Formula

The molecular formula shows the actual number of atoms of each element in one molecule. Elements are written using periodic table symbols, with subscript numbers showing how many atoms are present.

Example: Glucose — Molecular formula: C₆H₁₂O₆. This tells you one molecule of glucose has 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

Empirical Formula

The empirical formula shows the simplest whole-number ratio of atoms in a compound. It is derived from the molecular formula by dividing all subscripts by their highest common factor.

Example: Glucose — Empirical formula: CH₂O. This shows the ratio of C : H : O = 1 : 2 : 1.

Structural Formula

The structural formula shows how atoms are bonded together and their arrangement in the molecule. It identifies which atoms connect to which and tells you about the molecule's shape and bonding.

Example: Glucose — Structural formula shows the ring structure with carbon, hydrogen, and oxygen atoms connected by single bonds.

How to Write a Chemical Formula: Rules and Steps

Writing a chemical formula correctly depends on knowing the element symbols, valencies, and a few naming rules. These rules are tested in Class 9 and Class 10 boards. See NCERT Solutions Class 10 Science Chapter 1 for worked examples on writing formulas from compound names.

Most compounds are binary — they contain two elements. For compounds with a metal and a non-metal, write the metal first. Example: NaCl — Na⁺ is the cation (metal), Cl⁻ is the anion (non-metal).

Find the valency of each element. Make the sum of valencies equal by using subscripts — apply the criss-cross method. Anions with a -1 charge take the suffix -ide. Anions containing oxygen (oxyanions) take the suffix -ate.

Common polyatomic anions to remember:

Worked Example: Writing Al₂O₃

Oxygen valency = 2 (Group VI). Aluminium valency = 3 (Group III). LCM of 2 and 3 = 6. O needs subscript 3 (6 ÷ 2 = 3); Al needs subscript 2 (6 ÷ 3 = 2). Formula: Al₂O₃.

How to Balance a Chemical Equation

Balancing a chemical equation follows four rules. This section is tested in Class 10 Science Chapter 1 and frequently appears as a 2-mark question.

Write the correct formulas of all reactants on the left side of the arrow. Write the correct formulas of all products on the right side. Use + to separate multiple reactants or products. Balance atom counts by adding coefficients only — never change the subscripts.

Worked Example: Hydrogen and chlorine react to form hydrogen chloride.

Step 1: H₂ + Cl₂ → HCl (unbalanced — 2 H and 2 Cl on left, 1 H and 1 Cl on right) Step 2: Add coefficient 2 on the product side: H₂ + Cl₂ → 2HCl Step 3: Check — 2 H on both sides, 2 Cl on both sides. Balanced.

More real-world examples:

• Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O
• Iron rusting: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃
• Calcium carbonate formation: CaCl₂ + Na₂CO₃ → CaCO₃ + 2NaCl
• Hydrogen combustion: 2H₂(g) + O₂(g) → 2H₂O(l)

Important Chemistry Formulas: Quick Reference Table

The 30 most searched important chemical formulas across CBSE Class 9 to 12 and entrance exams. To calculate molar mass using any of these formulas, use the Molar Mass Formula guide on Extramarks.

Chemistry Formulas for Class 10

Class 10 Science Chapter 1 (Chemical Reactions and Equations) and Chapter 2 (Acids, Bases and Salts) are the two highest-weightage chemistry chapters in the 2026 CBSE board exam. These are the most important formulas from those chapters.

Chemistry Formulas for Class 11: Organic and Inorganic

Class 11 Chemistry introduces organic chemistry, thermodynamics, equilibrium, and redox reactions. The NCERT Solutions Class 11 Chemistry Chapter 1 page covers the foundational concepts. The Ideal Gas Law Formula is one of the most important physical chemistry formulas introduced in Class 11.

Inorganic Chemistry Class 11

Organic Chemistry Class 11

Chemistry Formulas for Class 12

Class 12 Chemistry includes electrochemistry, coordination compounds, biomolecules, and polymers. The CBSE Important Questions Class 12 Chemistry Chapter 1 page covers board-level problem types for this class.

Organic Chemistry Formulas

Students searching for organic chemistry formulas are usually preparing for Class 11, Class 12, or NEET. Organic compounds contain carbon. The most common organic chemistry formulas appear across hydrocarbons, alcohols, acids, and sugars.

Acids and Bases Chemistry Formulas

The acids and bases chapter appears in Class 10, 11, and NEET. Knowing the formula of each acid and base is the first step before writing any neutralisation reaction.

Common Acids

Common Bases

Chemistry Formulas for NEET

NEET Chemistry tests inorganic, organic, and physical chemistry across all three sections. These are the 15 most frequently tested compound formulas in NEET 2026.

Complete Chemical Formula List: 40 Most Searched Compounds

The table below lists 40 of the most searched chemical compound formulas from the full 260+ list on this page.