
#1
Oct2208, 10:51 PM

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 Z_{eff} = Z  S E=R_{H}(Z^{2}/n^{2}) ?? E=R_{H}(Z_{eff}^{2}/n^{2})?? 3. The attempt at a solution My attempted solution was subbing into Z_{eff} = Z  S Z_{eff} = 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 ? 



#2
Oct2308, 03:03 AM

Admin
P: 22,704

One of the equations you listed contains both ionization energy and effective nuclear charge, why don't you use it?




#3
Oct2308, 04:27 AM

P: 13

Ah..
So subbing in values E=899.4 kJ/mol R_{H}=2.178 x 10^{21} kJ n=1 I get Z^{2}_{eff}= 4.129 x 10 ^{23} mol How does one get to the units/value of Z^{2}_{eff} after this? 



#4
Oct2308, 04:53 AM

Admin
P: 22,704

calculating effective nuclear charge
Ionization energy was per mole, not per molecule.




#5
Oct2308, 05:17 PM

P: 13

Oops, just noticed that "Z^{2}_{eff}= 4.129 x 10 23 mol " should actually read "Z^{2}_{eff}= 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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