Rhodium ionization energy

Which element in each of the following sets has the highest ionization energy (a) phosphorus, arsenic, antimony (b) cadmium, rhodium, molybdenum ... 

In the rhodium case, considerable back donation appears to occur from the metal aj + a2 (e2) levels to the CO ligands as these orbitals show a greater ionization energy than the cpej orbitals. In the cobalt compound the I.E. ordering is the more conventional e2 < e t. 

Write equations that show the process for (a) the first two ionization energies of gallium and (b) the fourth ionization energy of rhodium. 

Fig. 9.8 (a) Energy-level diagram of Rh atom, and laser transitions used for selective ionization of this atom. Three dye-laser pulses raise 10% of Rh atoms to a Rydberg state with an effective principal quantum number of n fs 15 20 ns later, the highly excited atoms are ionized with an efficiency close to unity by means of an electric field pulse, (b) The first data on rhodium concentrations at the K/T boundary (in the Sumbar-SM-4 section, Turkmenia) obtained by the ultrasensitive laser photoionization spectroscopy technique. The maximum Rh concentration in the sample studied was 24.2 ng g . The Rh/Ir ratio was 0.34 0.06, which is close to the cosmic ratio of these elements. (Prom Bekov et al. 1988.)... 

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