Osmium ionization energy

On the basis of your knowledge of periodicity, place each of the following sets of elements in order of decreasing ionization energy. Explain your choices, (a) Selenium, oxygen, tellurium (b) gold, tantalum, osmium (c) lead, barium, cesium. 

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 ... 

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. 

The UPS spectra for these clusters reveal the general appearance of a 3-4 eV wide metal d band lying immediately below the Fermi level which is separated by 2-3 eV from an intense peak due to the CO 5intense peak at 3-4 eV below the 5a and l r features is due to the CO 4a levels. These spectra exhibit a remarkable qualitative similarity to the corresponding spectra of CO adsorbed on metal surfaces. More important for the present discussion is that they can be directly compared with the ionization energies obtained from theoretical calculations. For instance, the calculated spectra for a series of tetracobalt carbonyl clusters using the DV-Xa method have been compared with the He(I) UPS spectrum of [Co4(CO)i2]. [150] The transition state procedure [41] used in these calculations also accounted for the final state effects, that is, for the effects of orbital relaxation following the ionization process. This relaxation is typically about 2 eV for the valence orbitals of transition metal carbonyls and the calculated IP s compare well with the experimental ones. In a similar way, ruthenium, osmium, and rhenium carbonyl cluster UPS spectra have been calculated and reproduce the general trends and positions of the... 

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. 

Advances in spectroscopic characterization continue to drive the development of the field. A number of studies describing the mass spectrometry of medium- and high-nuclearity ruthenium and osmium carbonyl clusters have been reported, including UV-laser desorption, laser desorption/ionization time-of-flight and energy-dependent electrospray ionization the last mentioned has been shown to resolve mixtures of cluster compounds. 

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