Identifying the Polarity of Molecules?

📌 CONCEPT: The polarity of a molecule is determined by the difference in electronegativity between its atoms, the shape of the molecule, and the presence of polar bonds.

📐 RULE / FORMULA: The polarity of a molecule can be predicted using the electronegativity difference rule, where a difference of 0.4 or more between atoms results in a polar bond, and the shape of the molecule (symmetrical or asymmetrical) influences overall polarity.

💡 WORKED EXAMPLE: For the molecules of ammonia (NH3), water (H2O), and carbon dioxide (CO2), the electronegativity difference between N and H in NH3 is 0.9, between O and H in H2O is 1.4, and between O and C in CO2 is 0.4. Considering the shape, NH3 is trigonal pyramidal, H2O is bent, and CO2 is linear. Therefore, the order of increasing polarity is CO2 < NH3 < H2O.

⚠️ COMMON MISTAKE: Students often neglect the shape of the molecule when determining polarity, leading to incorrect conclusions about the overall polarity of the molecule.