Lecture Notes: Ionic and Covalent Bonding

Overview

• Discussion on the differences between ionic and covalent bonding.
• Key concepts of electron transfer and sharing in chemical bonds.

Ionic Bonding

• Definition: Electrons are transferred from one atom to another, resulting in ions.
• Example: Sodium (Na) and Chlorine (Cl).
  • Sodium: 1 valence electron (Group 1A), tends to lose one electron -> positive ion (Na⁺).
  • Chlorine: 7 valence electrons (Group 7A), tends to gain one electron -> negative ion (Cl⁻).
• Forces: Electrostatic attraction between opposite charges forms the ionic bond.
  • Opposite charges (positive and negative) attract each other.

Covalent Bonding

• Definition: Electrons are shared between atoms.
• Example: Hydrogen (H).
  • Hydrogen wants 2 electrons to fill its outer shell.
  • Shares electrons with another hydrogen atom, forming a covalent bond.
• Types of Covalent Bonds:
  • Non-polar Covalent Bond: Equal sharing of electrons, e.g., H-H bond.
  • Polar Covalent Bond: Unequal sharing of electrons, e.g., H-F bond.
    • Fluorine (F) is more electronegative, pulls electrons towards itself, creating partial charges.
    • Definition of electronegativity: Ability of an atom to attract electrons.

Differentiating Bond Types

• Ionic bond criteria: Metal + nonmetal.
  • Metals: Left side of periodic table.
  • Nonmetals: Right side of periodic table.
• Covalent bond criteria: Nonmetals sharing electrons.

Practice Problems

1. Magnesium Oxide (MgO)

   • Ionic because it’s metal (Mg) + nonmetal (O).
   • Magnesium gives 2 electrons to oxygen, forming ions.

2. Chlorine (Cl₂)

   • Non-polar covalent because it's two same nonmetals sharing electrons equally.

3. Sodium Fluoride (NaF)

   • Ionic bond: Metal (Na) + nonmetal (F).

4. Hydrogen Bromide (HBr)

   • Polar covalent: Different elements, calculate electronegativity difference (0.7).

5. Iodine Monobromide (IBr)

   • Non-polar covalent: Small electronegativity difference (0.3).

Additional Examples

• Carbon-Hydrogen (CH)

  • Generally non-polar covalent (electronegativity difference 0.4).

• Hydrogen-Oxygen (H-O)

  • Polar covalent due to hydrogen bonding, large electronegativity difference (1.4).

• Fluorine (F₂)

  • Non-polar covalent, same nonmetal, electronegativity difference (0).

• Calcium Sulfide (CaS)

  • Ionic, metal (Ca) + nonmetal (S).

Conclusion

• Understanding the nature of ionic and covalent bonds is crucial in chemistry.
• Different properties and behaviors arise from the type of bonding.
• Utilize periodic table and electronegativity values to differentiate bond types.