Nickel ionization energy

Identify the element with the higher first ionization energy in each of the following pairs (a) iron and nickel (b) nickel and copper (c) osmium and platinum (d) nickel and palladium ... 

C08-0023. Iron and cobalt form compounds that can be viewed as containing cations, but nickel does not. Use the ionization energies in Appendix C to predict which other transition metal elements are unlikely to form stable cations with charges greater than +2. 

Orbital Energies (eV), Population Analyses, and Ionization Energies (eV) for Bis(7r-allyl)nickel and Some of Its Ionsa... 

Experimental Ionization Energy Data (eV) for Bis(tr-allyl)nickel and Related Compounds0... 

Instead the critical factor is the overlap between cluster orbital of the same symmetry. In particular for on-top dissociation, a requirement of the on-top atom is an easily accessible atomic state with singly occupied 3d and 4s orbitals (5-7). When this condition is fulfilled, the on-top dissociation becomes the most favorable pathway. This is the reason why nickel succeeds and copper fails to break the H bond (7,8). The correlation between the ionization energies and the reactivities of the clusters is therefore, in our opinion, the most surprising of all the above mentioned experimental results. 

The increased ionization energies of the heavier transition metals should not be unexpected by anyone who has had a modicum of laboratory experience with any of these elements. Although none of the coinage metals is very reactive, gold has a well-deserved reputation for being less reactive than copper or silver iron, cobalt, and nickel rust and corrode, but osmium, indium, and platinum are noble and unreaclive and therefore are used in jewelry platinum wires are the material of choice fior flame tests without contamination and one generates hydrogen with zinc and simple adds, not with mercury. 

E.g., very accurate calculations on the nickel atom include the use of basis sets that extend up to 14s, 9p, and 5d as well as f orbitals. K. Raghavachari, G.W.Trucks, Highly Correlated Systems. Ionization Energies of First Row Transition Metals Sc-Zn, Journal of Chemical Physics, 91,2457-2460,1989. 

The first ionization energies of iron, cobalt, nickel, and the first three platinum metals are all about the same, but the first ionization energies of osmium, iridimn, and platinum are substantially greater. Suggest an explanation for this observation. 

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