The Nature of Bonding in Polyatomic Noble Gas Ions

A description of the electronic structure and the nature of bonding in polyatomic noble gas ions follows exactly the same lines pursued in the case of diatomic noble gas molecules (Sect. 4.5). Once the electronic wave function has been determined by ab initio calculations, the electron density distribution can be calculated, the MED path and (3, — 1) critical points can be found, and the properties of p(r) and H(r) can be evaluated at the critical points of p(r). This has been done for NgjX (X = C, N, O), NgCCNg +, NgCCH+, and NgCN+ ions. We will review in this section the results of these investigations [7, 13]. 

Dication State Bond Pt. [eA- ] Hb. [hartree A B. [kcal/mol] Nature of bonding 

A second He atom can not be bound in the same way. If two He atoms approach C ( S) from different sides, then the net distortion of this valence shell will be much smaller than in the case of HeC fX Z ) as can be seen from Fig. 16. As a consequence, the stability of He2C ( Aj) is due to electrostatic interactions such as charge-induced dipole attraction rather than covalent bonding [7]. 

Since the donor ability of Ng increases from He to Ar, both NejC l Aj) and Ar2C ( Ai) possess covalent bonds with increasing bond energies. This increase can also be observed for the other Ng2C ions (Table 14). 

Bonding in Ng2N + and Ng20 can be explained in the same way. In Fig. 17a and b, perspective drawings of the Laplace concentration of N ( P) and O ( D) are shown. Both dications possess concentration holes in their valence shell, which can be filled with electrons of a suitable donor. The holes correspond to low lying unoccupied 2p orbitals, which split into 2pa and 2pn 

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