Calculating effective nuclear charge

In summary, the effective nuclear charge for Be can be calculated using the equation Zeff = Z - S, where Z is the atomic number and S is the number of shielding electrons. By substituting the known values of ionization energy, Rydberg constant, and principal quantum number into the equation E=RH(Zeff2/n2), we can solve for Zeff, which has units of mol-1. It is important to note that ionization energy is given per mole, not per molecule, and thus the resulting units for Zeff are mol-1.
  • #1
escryan
13
0

Homework Statement



If ionization energy is 899.4 kJ/mol for Be, what is the effective nuclear charge?

Homework Equations


Zeff = Z - S

E=RH(Z2/n2) ??
E=RH(Zeff2/n2)??

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 ?
 
Physics news on Phys.org
  • #2
One of the equations you listed contains both ionization energy and effective nuclear charge, why don't you use it?
 
  • #3
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?
 
  • #4
Ionization energy was per mole, not per molecule.
 
  • #5
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...
 

1. How is effective nuclear charge calculated?

Effective nuclear charge is calculated by subtracting the number of inner shell electrons from the total number of protons in the nucleus. This takes into account the shielding effect of inner shell electrons on outer shell electrons.

2. Why is effective nuclear charge important?

Effective nuclear charge is important because it affects the attraction between the nucleus and valence electrons, which in turn influences the chemical and physical properties of an atom.

3. How does effective nuclear charge change across a period in the periodic table?

Effective nuclear charge generally increases across a period in the periodic table due to the increasing number of protons in the nucleus. This results in a stronger attraction between the nucleus and valence electrons.

4. What is the relationship between effective nuclear charge and atomic radius?

As effective nuclear charge increases, the atomic radius decreases. This is because the increased attraction between the nucleus and valence electrons pulls the outer electrons closer to the nucleus, making the atom smaller.

5. How does effective nuclear charge affect ionization energy?

Effective nuclear charge has a direct relationship with ionization energy. As it increases, the amount of energy required to remove an electron from an atom also increases. This is because the stronger attraction between the nucleus and valence electrons makes it more difficult to remove an electron.

Similar threads

  • Biology and Chemistry Homework Help
Replies
2
Views
1K
  • Biology and Chemistry Homework Help
Replies
1
Views
1K
  • Biology and Chemistry Homework Help
Replies
5
Views
3K
  • Biology and Chemistry Homework Help
Replies
6
Views
3K
  • Biology and Chemistry Homework Help
Replies
1
Views
5K
  • Biology and Chemistry Homework Help
Replies
1
Views
1K
  • Biology and Chemistry Homework Help
Replies
7
Views
1K
  • Biology and Chemistry Homework Help
Replies
6
Views
2K
  • Biology and Chemistry Homework Help
Replies
11
Views
3K
  • Biology and Chemistry Homework Help
Replies
5
Views
2K
Back
Top