Introduction to Drawing Lewis Structures

Understanding Valence Electrons

• Valence Electrons: Electrons in the outer shell of an atom.
  • Hydrogen: 1 valence electron
  • Beryllium: 2 valence electrons
  • Carbon: 4 valence electrons
  • Nitrogen: 5 valence electrons
  • Oxygen: 6 valence electrons
  • Fluorine: 7 valence electrons
• When drawing Lewis structures, only show the valence electrons.
• Electron Distribution: Space out electrons evenly before pairing them.

Simple Lewis Structures for Elements

• Hydrogen: Single dot representing 1 electron.
• Beryllium: Two dots.
• Carbon: Four dots.
• Oxygen: Six dots, with electrons spaced out.
• Fluorine: Seven dots.

Lewis Structures for Molecules

Hydrogen Gas (H2)

• Each hydrogen atom has 1 valence electron.
• Hydrogen forms a single bond (H-H).

Chlorine Gas (Cl2)

• Chlorine has 7 valence electrons.
• Forms a single covalent bond (Cl-Cl).
• Halogens like fluorine, chlorine, bromine prefer single bonds.

Understanding Bond Formation

• Carbon: Likes to form 4 bonds to satisfy 8 valence electron rule.
• Nitrogen: Forms 3 bonds to acquire 3 more electrons.
• Oxygen: Forms 2 bonds.
• Fluorine: Forms 1 bond.
• Boron and Beryllium: Prefer to give away their electrons forming fewer bonds.

Drawing Lewis Structures for Compounds

Oxygen Gas (O2)

• Each oxygen atom has 6 valence electrons.
• Forms a double bond (O=O).
• Remaining electrons form lone pairs.

Methane (CH4)

• Carbon has 4 valence electrons; hydrogen has 1.
• Forms 4 single bonds (CH4).

Ammonia (NH3)

• Nitrogen has 5 valence electrons.
• Forms 3 single bonds (NH3).
• Lone pair on nitrogen.

Water (H2O)

• Oxygen has 6 valence electrons.
• Forms 2 single bonds with hydrogen.
• Bent shape due to lone pairs.

Oxygen Difluoride (OF2)

• Oxygen forms 2 bonds, fluorine forms 1.
• Bent shape like water.

Complex Molecules

Hydrazine (N2H4)

• Nitrogen likes to form 3 bonds.
• Use lone pairs for remaining electrons.

Acetylene (C2H2)

• Carbon forms 4 bonds; hydrogen forms 1.
• Triple bond between carbon atoms.