Summary Chemical formula

Chemical Formulas, Molecular and
Ionic Substances notes

🧪 1. What is a Chemical Formula?
A chemical formula shows:

 The elements in a compound.
 The number of atoms of each element.

Examples:

 Water: H₂O → 2 hydrogen (H) + 1 oxygen (O)
 Carbon dioxide: CO₂ → 1 carbon (C) + 2 oxygen (O)




⚖️2. Types of Substances
Type Bond Type Made of Example
Molecular Covalent Non-metals + Non-metals H₂O, CO₂
Ionic Ionic Metals + Non-metals NaCl, MgCl₂
Elemental Pure elements One kind of atom O₂, Fe


🧬 3. Molecular Substances (Covalent Compounds)
 Atoms share electrons.
 Usually non-metals.
 Exist as individual molecules.
 Low melting/boiling points.
 Often liquids or gases at room temp.

Examples:

 H₂O → Water
 CH₄ → Methane
 NH₃ → Ammonia

📝 Naming Covalent Compounds:

Use prefixes to show the number of atoms:



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