Notes on Polarity and Covalent Bonds

Polarity and Covalent Bonds

• Covalent Bonds: Nonpolar

  • Identical atoms (e.g., H2, Cl2) share electrons equally.

  • Form pure/nonpolar covalent bonds.

  • Example: Cl2 → Cl + Cl (each Cl shares one electron).

  • Each Cl has 6 nonbonding electrons + 2 shared → 8 total (matches Argon's valence).

• Covalent Bonds: Polar

  • Different atoms share electrons unequally due to differing electronegativities.

  • This results in a polar covalent bond with partial charges.

  • Electron density shifts toward one atom: one becomes partially negative (δ–), the other partially positive (δ+).

  • Example: HCl molecule (H–Cl) – electrons spend more time near Cl.

  • Cl carries δ–; H carries δ+.

• Notation of Charges

  • Use lowercase Greek letter delta (δ) to denote partial charges:

  • δ+ indicates partial positive charge.

  • δ– indicates partial negative charge.

  • Electrons have uneven distribution in polar bonds (greater density near the more electronegative atom).

  • Visual: In HCl, electron density is greater around Cl; contrast with H2 where density is uniform and balanced.

• Visual Representation

  • Electron density seen around HCl is asymmetrical; shaded area larger around Cl than H.