Ionic compounds

[chiddler]

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Is it accurate to say that a dication-dianion is always more strongly bound than a mono-mono counterpart?

example, CaO versus KF.

What about KF versus Na2O? Which is stronger?

thanks.

 

[MedPR]

Is it accurate to say that a dication-dianion is always more strongly bound than a mono-mono counterpart?

example, CaO versus KF.

What about KF versus Na2O? Which is stronger?

thanks.

No because Coulomb's law; F=kq1q2/r^2. I don't know about KF vs Na2O.

 

[chiddler]

No because Coulomb's law; F=kq1q2/r^2. I don't know about KF vs Na2O.

got a question that asked which is strongest:

BaO, KF, AgCl, NaO2.

Answer is BaO because it has strongest ionic interactions. Besides looking at their ionic charges, what else could i be looking at?

i understand the answer superficially, but i'm not sure how to apply this to novel situations.

 

[MedPR]

got a question that asked which is strongest:

BaO, KF, AgCl, NaO2.

Answer is BaO because it has strongest ionic interactions. Besides looking at their ionic charges, what else could i be looking at?

i understand the answer superficially, but i'm not sure how to apply this to novel situations.

Well, I have no idea. I would've guessed KF. It makes sense that the dication/dianion might be stronger, but Barium's atomic radius is so much larger than Potassium..

 

[chiddler]

that's what i answered :-x

 

[SH3]

got a question that asked which is strongest:

BaO, KF, AgCl, NaO2.

Answer is BaO because it has strongest ionic interactions. Besides looking at their ionic charges, what else could i be looking at?

i understand the answer superficially, but i'm not sure how to apply this to novel situations.

Greatest difference in electronegativity?

 

[chiddler]

greatest difference in electronegativity?

is KF

 

[SH3]

is KF

Bond dissociation energies b/w BaO and KF?

is that out of scope of the Q?

 

[chiddler]

Bond dissociation energies b/w BaO and KF?

is that out of scope of the Q?

that is what my question is about

which has higher bond dissociation energy? or which is a stronger ionic bond?

 

[SH3]

that is what my question is about

which has higher bond dissociation energy? or which is a stronger ionic bond?

Hmm, I see. Where is the Q from? reputable source? Is it discrete or passage-based?

 

[chiddler]

Tpr

 

[SH3]

Tpr

It must be due to the fact that 2 electrons are involved in the bond (as you initially said) which creates a greater electrostatic force (coulomb's law) between the two electrons. This effect is greater than the difference in distance b/w Ba and O compared to K and F.

 

[chiddler]

maybe. that's probably it.

because the only way to offset two times more charge that is to reduce radius drastically (reduce by 1.4, if i'm not mistaken). i'm sure when it comes to atomic radii, the differences are very minute.

thanks a lot for your help

 

[MedPR]

Turns out Barium is not larger than Potassium even though it is lower on the periodic table (as per the atomic radius trend). So since the radii are about the same, but the charge is doubled, BaO is stronger than KF.

No way you could correctly answer this without knowing about the radii though...

 

[SH3]

maybe. that's probably it.

because the only way to offset two times more charge that is to reduce radius drastically (reduce by 1.4, if i'm not mistaken). i'm sure when it comes to atomic radii, the differences are very minute.

thanks a lot for your help

exactly; and because Barium is actually one over and only one below on the periodic table, this difference in size, even without knowing what MedPR said above, is very very minute.

no problem

 

[SH3]

Turns out Barium is not larger than Potassium even though it is lower on the periodic table (as per the atomic radius trend). So since the radii are about the same, but the charge is doubled, BaO is stronger than KF.

No way you could correctly answer this without knowing about the radii though...

what the what? but how? Greater pull on electrons due to one over in column (more protons)? still 2 extra shells?

 

[chiddler]

no wait. i'm wrong.

they could very well be half or double and such. the differences are not so minute when it comes to equations:

http://en.wikipedia.org/wiki/Atomic_radius#Empirically_measured_atomic_radii

However! The differences are noticeable when the two elements are very far apart/very different. In the case of K and Ba, we should be able to say that they are similar enough such that radius is not too significant. at least, not significant enough to be a magnitude of difference.

 

[SH3]

no wait. i'm wrong.

they could very well be half or double and such. the differences are not so minute when it comes to equations:

http://en.wikipedia.org/wiki/Atomic_radius#Empirically_measured_atomic_radii

wait writing more.

if you look at that periodic table, it actually shows the radius of Barium to be smaller than Potassium :|

 

[SH3]

no wait. i'm wrong.

they could very well be half or double and such. the differences are not so minute when it comes to equations:

http://en.wikipedia.org/wiki/Atomic_radius#Empirically_measured_atomic_radii

However! The differences are noticeable when the two elements are very far apart/very different. In the case of K and Ba, we should be able to say that they are similar enough such that radius is not too significant. at least, not significant enough to be a magnitude of difference.

Mhmm

 

[MedPR]

what the what? but how? Greater pull on electrons due to one over in column (more protons)? still 2 extra shells?

Yea, but coulomb's law is Kq1q2/r^2. So a dication-dianion will not have a stronger bond than a cation-anion if the cation-anion has a radius less than half as large.

 

[SH3]

Yea, but coulomb's law is Kq1q2/r^2. So a dication-dianion will not have a stronger bond than a cation-anion if the cation-anion has a radius less than half as large.

But that isn't the case in this question.

 

[MedPR]

But that isn't the case in this question.

I know, but it was the original question. I just wanted to mention that it's not safe to assume that BaO has a stronger bond than every anion-cation combination just because BaO is dicationic-dianionic.

 

[SH3]

I know, but it was the original question. I just wanted to mention that it's not safe to assume that BaO has a stronger bond than every anion-cation combination just because BaO is dicationic-dianionic.

Yep, good point to clarify for anyone reading this to ensure it shouldn't be taken out of context.