Chemical Formulas and Compounds

Introduction #

Chemical formulas are like a language that chemists use to describe molecules and compounds. They tell us what elements are present in a compound and how many atoms of each element we have. Understanding how to write and interpret chemical formulas is fundamental to chemistry.

Writing Chemical Formulas #

Basic Rules #

1. Elements and Symbols

• Each element has a unique symbol (e.g., Na for Sodium, Cl for Chlorine)
• The first letter is always s Capital Letter
• If there’s a second letter, it’s lowercase

1. Numbers in Formulas

• Numbers written just below each atom/compound, show how many atoms of each element
• If no number is written, it means there’s one atom

Examples from Questions #

Let’s look at some examples from Question 1:

1. Silver Chloride (AgCl)

• Made from Ag⁺ and Cl⁻
• One silver ion combines with one chloride ion
• Simple 1:1 ratio gives AgCl

1. Calcium Carbonate (CaCO₃)

• Made from Ca²⁺ and CO₃²⁻
• One calcium ion combines with one carbonate ion
• Formula becomes CaCO₃

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