Effective Nuclear Charge

[MedPR]

Why does effective nuclear charge increase from left to right across the periodic table?

Zeff=Z-shielding electrons.

As you move to the right, Z increases, but don't the number of shielding electrons increase as well? I might be answering my own question here, but does Zeff increase because the change in the nuclear charge from left to right is more significant than the additional shielding effects? If so, why?

Is it because as you move left to right you typically are adding an electron to the same orbital (except when you transition from metals to transition metals and transition metals to nonmetals)? So the addition electron isn't actually contributing to the shielding effect since it is being added to the outermost orbital?

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[chiddler]

I think what you wrote last is correct. I'm not too certain about this and would like to be corrected if inaccurate: I think about it as the simplistic high school picture of valence electrons. No s p or d orbitals, just 2👎^2 valence electrons in linear shells.

With this image, electron shielding is easy to imagine. Higher atomic # doesn't increase shielding, only effective nuclear charge.

 

[MrNeuro]

Why does effective nuclear charge increase from left to right across the periodic table?

Zeff=Z-shielding electrons.

As you move to the right, Z increases, but don't the number of shielding electrons increase as well? I might be answering my own question here, but does Zeff increase because the change in the nuclear charge from left to right is more significant than the additional shielding effects? If so, why?

Is it because as you move left to right you typically are adding an electron to the same orbital (except when you transition from metals to transition metals and transition metals to nonmetals)? So the addition electron isn't actually contributing to the shielding effect since it is being added to the outermost orbital?

if i remember correctly its because the extra proton has a greatest effect on Zeff

 

[Dasypus]

Why does effective nuclear charge increase from left to right across the periodic table?

Zeff=Z-shielding electrons.

As you move to the right, Z increases, but don't the number of shielding electrons increase as well? I might be answering my own question here, but does Zeff increase because the change in the nuclear charge from left to right is more significant than the additional shielding effects? If so, why?

Is it because as you move left to right you typically are adding an electron to the same orbital (except when you transition from metals to transition metals and transition metals to nonmetals)? So the addition electron isn't actually contributing to the shielding effect since it is being added to the outermost orbital?

You have it about right in the last thing you say. Within a block, the additional electron is put into orbit in an existing shell, so at the same distance as the valence electrons that were in the previous element. Electrons that are 'next to' each other like that can't shield each other from the nucleus's charge. Only the electrons between them and the nucleus can cancel out some of the charge they feel. As you go up the row, add more electrons in that outer shell, you aren't adding anything in between them and the nucleus, but you are adding an extra proton to that nucleus, the charge of which doesn't get really get shielded. Thus all the outer electrons feel more pull. And it's the pull on the outermost, valence electrons that Zeff measures.

 

[MedPR]

Ok thanks everyone. So within the same column the effective nuclear charge would decrease as you go down because you have more inner orbitals? 3s, 4s, etc?

 

[MrNeuro]

Ok thanks everyone. So within the same column the effective nuclear charge would decrease as you go down because you have more inner orbitals? 3s, 4s, etc?

yeah sort of and i also think it has to do with the atom just getting larger and b/c Zeff is found using Coloumbs law

 

[thestrokes14]

Ok thanks everyone. So within the same column the effective nuclear charge would decrease as you go down because you have more inner orbitals? 3s, 4s, etc?

No. Effective nuclear charge increases doing down and to the right. It basically increases with atomic number.