alkene (thing)

The general formula for unsubstituted alkenes is C_nH_2n

H     H
 \   /
  C=C
 /   \
H     H

 Ethene C2H4


H     H
 \    |
  C=C-C-H
 /  | |
H   H H

  Propene C3H6


H     H H               H     H
 \    | |               |     |
  C=C-C-C-H           H-C-C=C-C-H
 /  | | |               | | | |
H   H H H               H H H H

 1-Butene C4H8          2-Butene C4H8