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
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Updated January 28, 2026
Decoding Molecular Formulas
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
- 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!
Try Element-Based Search