Class 9 Science Chapter 3: Concepts

Writing Chemical Formulas

📅 Published: 30 March, 2025 🔁 Updated: 31 March, 2025 🕒 Read: 1 min

Writing Chemical Formulas

Rules for Writing Chemical Formulas

  1. Identify the symbols of elements.

  2. Determine the valency of each element.

  3. Cross-multiply the valencies to balance the formula.

Valency and Examples

  • Valency is the combining capacity of an element.

Valency Table of Common Elements

Element Symbol Valency
Hydrogen H 1
Oxygen O 2
Nitrogen N 3
Carbon C 4
Sodium Na 1
Chlorine Cl 1

Examples of Chemical Formulas:

  • Water (H₂O) → H (1) and O (2) → H₂O

  • Ammonia (NH₃) → N (3) and H (1) → NH₃

  • Calcium Chloride (CaCl₂) → Ca (2) and Cl (1) → CaCl₂

(Diagram: Valency table and chemical formula examples)

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