Effective Nuclear Charge?

[csx]

Im looking to compare the Z(eff) of F and S. I understand Z(eff) increases from left to right but I thought S had a greater Z(eff) because its in a higher period with an extra shell.

I want to compare the two mathematically to convince myself that F has a higher Z(eff) but idk how.

can someone explain this reasoning to me WHY F is greater than S?

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[Teleologist]

First define Z eff. From your reasoning it's clear that you don't know what Z eff is.

 

[csx]

First define Z eff. From your reasoning it's clear that you don't know what Z eff is.

Zeff affects how tightly bound the electrons are. More protons added to the same subshell=higher Zeff. I get why F has the highest in it's period.
I get why S has a higher zeff than the elements to the elements to its left. But I figured since it had more protons, so it pulls its electrons in more.

Or am I completely off base? if so, can you correct me?

 

[Teleologist]

S has another shell of electrons compared to F. Electron-shell shielding reduces the effective nuclear charge (Z eff). Yes, there are more protons in S, but there is also another shell of electrons in S. Z eff trends tend to only work across periods not up and down the table.

 

[csx]

S has another shell of electrons compared to F. Electron-shell shielding reduces the effective nuclear charge (Z eff). Yes, there are more protons in S, but there is also another shell of electrons in S. Z eff trends tend to only work across periods not up and down the table.

That makes sense. Would that mean that it decreases as you go down the periodic table due to more and more shells being added (exceptions excluded)?

 

[Teleologist]

That makes sense. Would that mean that it decreases as you go down the periodic table due to more and more shells being added (exceptions excluded)?

Yes.

 

[premed1001]

Yes.

Doesn't z effective the stay same moving down? And change only moving left or right?

 

[Teleologist]

Doesn't z effective the stay same moving down? And change only moving left or right?

No and yes.

 

[Czarcasm]

Doesn't z effective the stay same moving down? And change only moving left or right?

The important thing to know about Zeff is that it's primarily responsible for the trend in atomic radii. As you mentioned, Zeff increases within a period from left to right because we increase the number of protons (while maintaining the same number of core electrons). The downward trend you are referring to is due to shell size (increasing) and has nothing to do with the periodic trend described by Zeff. The only other instance where Zeff plays a major role in the sizes of different atomic radii (other than within a given period), is for an isoelectronic series. This series is simply a group of cations/anions that all share the same number of valence electrons (all have an octet) but different number of protons. Therefore, the smallest species would be the cation of the isoelectronic species with the greatest + charge (and the largest, the anion with the greatest - charge).

 

[Czarcasm]

No and yes.

These types of one word responses aren't helping anybody.

 

[premed1001]

The important thing to know about Zeff is that it's primarily responsible for the trend in atomic radii. As you mentioned, Zeff increases within a period from left to right because we increase the number of protons (while maintaining the same number of core electrons). The downward trend you are referring to is due to shell size (increasing) and has nothing to do with the periodic trend described by Zeff. The only other instance where Zeff plays a major role in the sizes of different atomic radii (other than within a given period), is for an isoelectronic series. This series is simply a group of cations/anions that all share the same number of valence electrons (all have an octet) but different number of protons. Therefore, the smallest species would be the cation of the isoelectronic species with the greatest + charge (and the largest, the anion with the greatest - charge).

that makes sense, thanks!

 

[Teleologist]

These types of one word responses aren't helping anybody.

Speak for yourself 😉.

 

[Czarcasm]

Speak for yourself 😉.

I'm not trying to be rude, but from what I gathered the past few days, reading some of your replies, ...it comes off a little condescending. Then again it's the internet. Sometimes things can be misconstrued.