• Three Sigma Bonds: For each carbon atom in double bond, three of the four electrons are used in
three σ- bond/ sigma bond.
• One Pi Bond: One electron left in p- orbital. Sideways overlap of two p orbitals on each carbon
atom forms π-bond above and below plane of molecule. The π- electron density is concentrated
here. Pi bond needs to labelled on diagram below.
• Rotation: The π- bond prevents the two C atoms rotating around double bond. Rotation is possible
around every other atom.
• Shape: Trigonal planar shape around each C atom, three areas of electron density equally repel
each other so bond angle around each C atom is 120.
• Simplify alkene to four groups. Do full structure before shortening to avoid mistakes. Always start
from double bond and draw outwards.
• When shortening, have H from the carbons of the double bond by themselves. Then have rest of
molecule in other space.
• Remember to leave the two gaps per double bond.
