Lecture Notes on Covalent Bonds

Introduction to Covalent Bonds

• Previous discussion on ionic bonds (electrons are stolen).
• Covalent bonds involve sharing electrons between atoms.

Oxygen Atoms and Covalent Bonding

Structure of Oxygen

• Each oxygen has:
  • Total Electrons: 8
  • Valence Electrons: 6
  • Arrangement of Electrons: 2 paired, 4 unpaired (unpairing occurs last).

Sharing Electrons

• Two oxygen atoms can share electrons to become more stable:
  • Oxygen on the left shares 2 electrons with oxygen on the right.
  • Oxygen on the right shares 2 electrons with oxygen on the left.

Representation of Covalent Bond

• Shared electrons are represented by a line:
  • One line = 2 shared electrons.
  • Example: 2 shared pairs of electrons between the two oxygens.

Result of Covalent Bonding

• Each oxygen effectively has 8 electrons (octet rule).
• Forming a covalent bond allows both oxygens to be more stable.

Examples of Covalent Bonds in Water

Oxygen and Hydrogen

• Oxygen has 6 valence electrons:
  • Example: Oxygen with electrons drawn out.
• Hydrogen has 1 valence electron:
  • Two hydrogen atoms (each with 1 electron).

Formation of Water Molecule

• Covalent bonds between oxygen and hydrogen:
  • Oxygen shares an electron with each hydrogen (2 total).
  • Each hydrogen shares its electron with oxygen.

Electronegativity and Polarity

• Oxygen is more electronegative than hydrogen (pulls electrons closer).
• Results in:
  • Partial Negative Charge on oxygen.
  • Partial Positive Charge on hydrogens.
• Represented by the Greek letter delta (δ) for partial charges.

Polar Covalent Bond

• Due to differences in electronegativity, the bond is polar.
• Polar Covalent Bond: One side has more charge than the other.