Ion size

[MedStudentWanna]

Can someone explain ion size to me in a way that makes me understand it instead of memorizing the protons the smaller it is?

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[MedStudentWanna]

Someone must be able to explain this.

 

[deleted109597]

Perhaps if you asked in a manner conducive to being answered.
I honestly can't even tell what you are asking.

Ions are smaller as you go up and to the right on the periodic table. Does that come close?

 

[MedStudentWanna]

Yes. Can you explain why they get smaller as you go to the right? I would have thought it was the opposite. I can memorize that it is how it is, but I don't really understand.

 

[chemnerd31]

The ions get smaller as you go from left to right due to the increase in the number of protons while the electrons are being placed in the outer valence shell. Remember the equation Zeff = Z-S where Zeff is the effective nuclear charge. Z is the number of protons and S is the number of inner core electrons. As you move from left to right Z increase but S does not and this leads to a larger Zeff. This increased Zeff is what caused the ions to shrink. The increase from top to bottom is because of naturally larged shells as the principal quantum number increases. I hope this helps

 

[chemnerd31]

Sorry double post

 

[MedStudentWanna]

Thank you, I get it now!!!

 

[BerkReviewTeach]

Not to drop a rain cloud over the parade, but that explanation describes why atoms get smaller as you move left-to-right across the periodic table. As Chemnerd explained, the nuclear pull increases and causes the electron cloud to contract, reducing the size of the cloud.

But, to answer your question about ion size, you need to first consider whether it is an anion or a cation. In a simplistic model, consider the impact of adding an extra electron to an atom to form an anion. The extra electron would repel the other electrons in the cloud, and it would expand. This explains why anions are bigger than the neutral atom. On the other hand, removal of an electron to form a cation results in a decrease in electron repulsion. This allows the electron cloud to contract, resulting in a smaller species. This means that cations are smaller than the nuetral element. Another factor that comes into play is the shell. If the electron being removed happens to be the last one in the shell, then the impact of size reduction is event greater, because a shell has been lost. This explains why alkali metal cations are so much smaller than their neutral element counterparts.

Hopefully this answers your question, assuming you meant ions when you typed it.

 

[MedStudentWanna]

I thought I understood it, but I guess no. I guess I just have to read more about it to truly understand.

 

[chemnerd31]

Thanks for adding that Berk I forgot that part when I wrote my reason.

 

[Doctor D]

Ions that have a negative charge are much larger than their neutral or positive counterparts (Cl- is > in size than Cl or Cl+). This is because the effective nuclear force exerted on the electrons by the protons in the nucleon is diluted by the addition of the extra electron. Since the electron feels less pull towards the center of the atom, it can wander farther away.