Calculating effective nuclear charge

by escryan
Tags: charge, effective, nuclear
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 P: 13 1. The problem statement, all variables and given/known data If ionization energy is 899.4 kJ/mol for Be, what is the effective nuclear charge? 2. Relevant equations Zeff = Z - S E=RH(Z2/n2) ?? E=RH(Zeff2/n2)?? 3. The attempt at a solution My attempted solution was subbing into Zeff = Z - S Zeff = 4 - 2 = 2 But I suspect that is wrong... because why ionization energy is given.. so shouldn't it be used in the calculation? And somewhere I think I read that "S" was supposed to be a "constant" of some sort, and I just subbed 2 in because I thought that it was the number of electrons in the first orbital ?
 Admin P: 23,716 One of the equations you listed contains both ionization energy and effective nuclear charge, why don't you use it?
 P: 13 Ah.. So subbing in values E=899.4 kJ/mol RH=2.178 x 10-21 kJ n=1 I get Z2eff= 4.129 x 10 23 mol How does one get to the units/value of Z2eff after this?
 Admin P: 23,716 Calculating effective nuclear charge Ionization energy was per mole, not per molecule.
 P: 13 Oops, just noticed that "Z2eff= 4.129 x 10 23 mol " should actually read "Z2eff= 4.129 x 10 23 mol-1 " I think that the italicized part is what confuses me the most -- what are the units for this portion? I'm going to take a guess that it is currently molecules/mol, but if so, is this always the case whenever expressing a value and the unit mol-1? Like for this example, what was given was in kJ/mol. When the kJs were cancelled, what resulted was just mol-1...

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