The Diatomic Hydrides of Periods 2 and

The value of the electron density at this point, the bond critical point density pt,. 

The shape of the electron density distribution in a plane through the bond critical point and perpendicular to the bond as measured by its ellipticity e. 

The position of the bond critical point. The distance of this point from each of the nuclei is a measure of the size of each atom, that is, its bonding radius rb. 

we illustrate these properties by discussing them together with some of the atomic properties for the diatomic hydrides of the elements of periods 2 and 3. 

9 The Diatomic Hydrides of Periods 2 and 3 6.9.1 Bond Critical Point Density 

The bonding radius of A in a diatomic hydride AH at first decreases across a period and then increases because there is a competition between two opposing effects  

---