Nodal plane, definition

This expression indicates that there is a decreased probability (indicated by the term —2(/>A(/>B) of finding the electrons in the region between the two nuclei. In fact, there is a nodal plane between the positive and negative (with respect to algebraic sign) of the two regions of the molecular orbital. As a simple definition, we can describe a covalent bond as the increased probability of finding electrons between two nuclei or an increase in electron density between the two nuclei when compared to the probability or density that would exist simply because of the presence of two atoms. 

An alternative definition for a and tt bonds is based on the number of nodal planes that are parallel to the bond axis a tr bond has no nodal planes parallel to the bond axis and a tt bond has 1 such nodal plane. 

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