Electrons in bonds remain localized between two atoms. electrons in bonds can become delocalized between more than two atoms.

Electrons in sigma bonds remain localized between two atoms. Sigma bond results from the formation of a molecular orbital by the end to end overlap of atomic orbitals. Electrons in pi bonds can become delocalized between more than two atoms. Pi bonds result from the formation of molecular orbital by side to side overlap of atomic orbitals. 

well off of my head we know that the perfume bottle is most likely opened, or broken. i can also tell it is moving at low and high concentration because it is covering the other side of the room. what we can obtain from this information is it explains why the odor can be detected at the other side of the room.