Chemistry Basics

The Science of Molecular Formulas: What They Tell Us

Understand how to read molecular formulas and what information they contain about chemical compounds.

4 min read|Updated January 28, 2026

Decoding Molecular Formulas

Every compound in our database has a molecular formula. Here's how to read and understand them.

Basic Format

A molecular formula shows: - Which elements are present (using chemical symbols) - How many atoms of each element (using subscript numbers)

Example: H₂O (Water) - H = Hydrogen - 2 = Two hydrogen atoms - O = Oxygen (no number means 1)

Reading Complex Formulas

C₆H₁₂O₆ (Glucose) - 6 Carbon atoms - 12 Hydrogen atoms - 6 Oxygen atoms

NaCl (Table Salt) - 1 Sodium atom - 1 Chlorine atom

Fe₂O₃ (Rust) - 2 Iron atoms - 3 Oxygen atoms

What Formulas Don't Tell You

Molecular formulas show composition but not: - How atoms are arranged (structure) - Types of bonds between atoms - 3D shape of the molecule

Two compounds can have the same formula but different structures (isomers).

Why Element-Based Search Matters

Traditional databases require you to know formulas like C₆H₁₂O₆. But: - You might not know the exact formula - You might want to explore possibilities - Memorizing formulas isn't practical

CompoundLookup solves this by letting you select elements (C, H, O) and see ALL matching compounds—including C₆H₁₂O₆ and every other carbon-hydrogen-oxygen compound.

Formula Patterns to Know

Hydrocarbons - CₙH₂ₙ₊₂ = Alkanes (methane, ethane, propane) - CₙH₂ₙ = Alkenes (ethylene, propylene)

Alcohols - CₙH₂ₙ₊₁OH = Primary alcohols (methanol, ethanol)

Organic Acids - RCOOH pattern = Carboxylic acids (acetic acid, citric acid)

Understanding these patterns helps, but with CompoundLookup, you don't need to memorize them—just explore!

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