Chemical Bonds

Introduction to Molecules and Atoms

• Molecules are made up of atoms that participate in chemical bonds.
• The key to bond formation is the difference in electronegativity between atoms.

Types of Chemical Bonds

1. Ionic Bonds

   • Formed when the electronegativity difference is greater than 2.
   • Example: Sodium (Na) and Chlorine (Cl).
     • Chlorine steals an electron from sodium.
     • Result: Sodium ion (Na+) and Chloride ion (Cl-).
   • Strong electrostatic attraction between ions of opposite charge.
   • Key Point: Electrons are taken, not shared.

2. Covalent Bonds

   • Formed when the electronegativity difference is less than 1.7.
   • Atoms share electrons rather than one atom stealing them.
   • Types of Covalent Bonds:
     • Polar Covalent Bonds
       • Electronegativity difference between 0.5 and 1.7.
       • Example: Hydrogen (H) and Chlorine (Cl).
       • Chlorine hogs the electrons leading to a partial charge.
       • Chlorine: partially negative (Δ-), Hydrogen: partially positive (Δ+).
     • Nonpolar Covalent Bonds
       • Electronegativity difference less than 0.5.
       • Electrons are shared evenly, or precisely evenly in cases of identical atoms.
       • No partial charges present.

Summary of Bond Predictions

• Nonpolar Covalent Bond:
  • Electronegativity difference < 0.5
  • Electrons shared evenly.
• Polar Covalent Bond:
  • Electronegativity difference between 0.5 and 1.7
  • Electrons shared unequally; one atom holds them more tightly.
• Ionic Bond:
  • Electronegativity difference > 2
  • One atom steals an electron, forming ions that bind via electrostatic attraction.

Conclusion

• Understanding electronegativity differences allows prediction of bond types.
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