Orbital lobe
(lobe): A section of orbital
bordered by one or more orbital
nodes.
The π
orbital of ethylene
has two orbital
lobes (one shown in the red and the other in blue), and one orbital
node (the plane which contains the atoms).
The π*
orbital of ethylene
has four orbital
lobes (one above and below the molecular
plane on each carbon), and two orbital
nodes (the plane which contains the atoms, and another
plane, perpendicular to the first, and bisecting the molecule).