Chemical Bonding Lecture Notes

Introduction to Chemical Bonding

• Importance of chemical bonding in chemistry; used in many chapters.
• Aim: To simplify the concept for better understanding.
• Analogy: Friendship bonds provide stability in life; similarly, atoms form bonds for stability.

Why Atoms Form Chemical Bonds

• Atoms combine to form molecules of elements and compounds.
• Main reason: Stability.
• Jenga Game Analogy: Stability in atoms compared to the stability of a Jenga tower.

Stability in Atoms

• Electronic Configuration: Arrangement of electrons in an atom.
  • Example: Atom with
    • 2 electrons in the first shell
    • 4 electrons in the second shell: 2, 4
    • Another atom with 8 electrons in the second shell: 2, 8
• Stability Rules:
  • Duplet Rule: For atoms with one shell, stability is achieved with 2 electrons.
  • Octet Rule: For atoms with more than one shell, stability is achieved with 8 electrons in the outermost shell.

Identifying Atoms Based on Stability

• Example Atoms:
  • Atom with 2, 4: Carbon (unstable)
  • Atom with 2, 8: Neon (noble gas, stable)

Types of Chemical Bonds

• Ionic Bonds: Also known as Electrovalent bonds
• Covalent Bonds: Also known as Molecular bonds
• Coordinate Bonds: Also known as Dative bonds

Ionic Bonds (Electrovalent Bonds)

• Involves transfer of electrons.
• Example: Sodium (Na) and Chlorine (Cl)
  • Sodium gives away 1 electron, becomes Na⁺ (cation).
  • Chlorine gains 1 electron, becomes Cl⁻ (anion).
• Resulting in Ionic Bond due to attraction of opposite charges.

Electron Dot Structure for Ionic Bond

• Show only valence electrons.
• Use arrows to indicate transfer of electrons.
• Example: [ Na^+ ] and [ Cl^- ] results in [ NaCl ].

Conditions for Ionic Bond Formation

• Usually occurs between metals and non-metals.
• Metals tend to lose electrons, while non-metals tend to gain electrons.
• Example: Magnesium (Mg) and Chlorine (Cl) form [ MgCl_2 ] via ionic bonding.

Covalent Bonds

• Involves sharing of electrons.
• Example: Hydrogen (H) atoms share electrons to form H₂ (molecular bond).
• Represented by a single line between atoms.
• Example: Oxygen (O) forms O₂ through sharing of two pairs of electrons (double covalent bond).

Electron Dot Structure for Covalent Bond

• Show valence electrons with dots and crosses.
• Example: H₂ structure shows shared pair of electrons.

Differences Between Ionic and Covalent Compounds

• Ionic Compounds:

  • Hard solids with high melting/boiling points.
  • Good conductors in molten/aqua state.
  • Soluble in water but insoluble in organic solvents.

• Covalent Compounds:

  • Usually gases, liquids, or soft solids with low melting/boiling points.
  • Non-conductors in any state.
  • Insoluble in water but soluble in organic solvents.

Conclusion

• Reviewed types of chemical bonding: ionic and covalent.
• Importance of understanding bonding for stability.
• Encouragement to explore further courses on various subjects including coding, physics, and chemistry.