Molecules, Compounds, and Their Types

Compounds 

- When molecules are made up of different elements, they are called compounds.  

- Example: H₂O (water), CO₂ (carbon dioxide).  

Molecules  

- Molecules can be diatomic (two atoms) or polyatomic (more than two atoms).  

- The molecular formula shows the actual number of atoms of each element that combine to form a molecule.  

Diatomic Molecules  

- Consists of two atoms of the same or different elements.  

- Examples: Hydrogen (H₂), Oxygen (O₂), Nitrogen (N₂), Fluorine (F₂), Chlorine (Cl₂).  

Polyatomic Molecules  

- Consists of more than two atoms.  

- Examples:  

  - Phosphorus (P₄) 

  - Sulphur (S₈)  

Polyatomic Molecules (Gases)  

- Ammonia (NH₃) 

- Methane (CH₄)  

- Ethane (C₂H₆)  

- Ethene (C₂H₄)  

- Ethyne (C₂H₂)  

- Carbon dioxide (CO₂)  

- Carbon tetrafluoride (CF₄)  

Polyatomic Molecules (Solids/Powders)  

- Silicon dioxide (SiO₂)  

Polyatomic Molecules (Liquids/Water)  

- Water (H₂O)  

Insight:  

Molecules form the building blocks of matter. Whether simple diatomic gases like oxygen or complex polyatomic compounds like silicon dioxide, their structure determines their physical state and chemical behaviour.