Draw the electron-dot structure of methane (CH4) and Ethane (C2H6).

Answer: In methane the carbon atom forms four C–H bonds (four shared pairs); in ethane each carbon forms three C–H bonds and one C–C bond. There are no lone pairs on any carbon atom.

(Carbon electrons are shown as •, hydrogen electrons as x. Each •x pair is one shared electron pair, i.e. one single covalent bond.)

Methane (CH₄):

          H
          x
          •
    H x • C • x H
          •
          x
          H

      H
      |
  H - C - H
      |
      H

Ethane (C₂H₆):

          H     H
          x     x
          •     •
    H x • C • • C • x H
          •     •
          x     x
          H     H

      H   H
      |   |
  H - C - C - H
      |   |
      H   H

In methane, carbon (2, 4) shares its four valence electrons with four hydrogen atoms, forming four single covalent bonds; carbon completes its octet and each hydrogen its duplet.

In ethane, the two carbon atoms share one pair of electrons (one from each carbon) to form a C–C single bond, and each carbon shares its remaining three electrons with three hydrogen atoms. So ethane has 7 shared pairs (one C–C and six C–H) and every carbon has an octet made only of bonding (shared) pairs.