Lewis Structures

Dot structures, bonding pairs, and lone pairs

Lewis structures represent the valence electrons in a molecule as dots and lines. A single bond is one shared electron pair (2 e⁻), a double bond is two pairs (4 e⁻), and a triple bond is three pairs (6 e⁻). The octet rule states most atoms want 8 electrons in their valence shell (H wants 2). Steps: (1) Count total valence electrons, (2) Place single bonds between bonded atoms, (3) Complete octets on terminal atoms with lone pairs, (4) Use remaining electrons on the central atom, (5) If central atom lacks an octet, convert lone pairs to multiple bonds. Formal charge = valence e⁻ − lone pair e⁻ − ½(bonding e⁻). Structures with formal charges closest to zero are most stable. Some molecules have resonance structures — multiple valid Lewis structures that differ only in electron placement.