Key Concepts of Lewis Structures and the Octet Rule

Lewis Structures

• Used to indicate formation of covalent bonds.

• Illustrates bonding in molecules and polyatomic ions.

• Example: Chlorine molecule (Cl2) has one shared pair of electrons and three lone pairs per Cl atom.

• A dash indicates a shared pair (single bond).

• Each Cl atom interacts with eight valence electrons (octet): 6 from lone pairs, 2 from the single bond.

Octet Rule

• Main group atoms tend to form enough bonds to reach eight valence electrons or two in the first shell (octet rule).

• Number of bonds predicted by the electrons required to complete an octet, particularly for nonmetals (C, N, O, F).

• Group 14 elements can form four covalent bonds to reach an octet (e.g., C in CCl4).

• Hydrogen: needs 2 electrons; forms one covalent bond.

• Group 15 (e.g., N) has 5 valence electrons; forms three covalent bonds (e.g., NH3).

• Group 16 (e.g., O) forms two covalent bonds for an octet.

• Group 17 (e.g., F) forms one covalent bond to complete the octet.

Multiple Bonds

• Single Bond: One pair of electrons shared.

• Double Bond: Two pairs of electrons shared (e.g., CH2O, C2H4).

• Triple Bond: Three pairs of electrons shared (e.g., CO, CN⁻).