Compare Ethane, Ethene, and Ethyne (Lewis Structures, Bonds, and Shapes)

1) Ethane (C₂H₆) — Alkane

• Total valence electrons: 14
• C–C bond: single bond (1 bonding pair)
• Lewis structure: each carbon is bonded to the other carbon and three hydrogens

    H   H
    |   |
H – C – C – H
    |   |
    H   H
    

Geometry: each carbon is sp³-hybridized → tetrahedral around each C (overall 3D).

2) Ethene (C₂H₄) — Alkene

• Total valence electrons: 12 (two fewer than ethane)
• C–C bond: double bond (2 bonding pairs) to satisfy octets with fewer hydrogens
• Lewis structure: the carbons are double-bonded; each carbon is bonded to two hydrogens

    H   H
    |   |
    C = C
    |   |
    H   H
    

Geometry: each carbon is sp²-hybridized → trigonal planar at each C (molecule is planar).

3) Ethyne (C₂H₂) — Alkyne

• Total valence electrons: 10 (four fewer than ethane)
• C–C bond: triple bond (3 bonding pairs) to satisfy octets with only one hydrogen per carbon
• Lewis structure: the carbons are triple-bonded; each carbon is bonded to one hydrogen

H – C ≡ C – H
    

Geometry: each carbon is sp-hybridized → linear (180°) overall.

Key Comparison

• C–C bonding progression: single → double → triple (ethane → ethene → ethyne).
• Valence electron counts: 14 → 12 → 10 (fewer hydrogens require more C–C bonding).
• Bond strength/length: triple > double > single (strength); single > double > triple (length).
• Hybridization & shape: sp³ (tetrahedral, 3D) → sp² (trigonal planar, flat) → sp (linear).