Atomic Radius

[ericyan3000]

Which of the following would have the greatest atomic radius?

A. Ca2+ (calcium ion)

B. Ar

C. Cl- (chloride ion)

They are all in 2, 8, 8 with the same number of electrons but with different number of protons. So I would rank them as A<B<C. Is this correct? Thanks.

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[osimsDDS]

They all have the same number of electrons but you have to compare the protons here...Ca has 20, Ar has 18, and Cl has 17. You added 1 electron to chlorine so it will most likely be the largest, Ar will be in the middle, and Calcium you lost 2 electrons from the s subshell so it will be the smallest due to the fact that it has the most protons pulling in the same number of electrons as the other 2...

hope that helps

 

[Mstoothlady2012]

Which of the following would have the greatest atomic radius?

A. Ca2+ (calcium ion)

B. Ar

C. Cl- (chloride ion)

They are all in 2, 8, 8 with the same number of electrons but with different number of protons. So I would rank them as A<B<C. Is this correct? Thanks.

I think its right!

 

[ericyan3000]

They all have the same number of electrons but you have to compare the protons here...Ca has 20, Ar has 18, and Cl has 17. You added 1 electron to chlorine so it will most likely be the largest, Ar will be in the middle, and Calcium you lost 2 electrons from the s subshell so it will be the smallest due to the fact that it has the most protons pulling in the same number of electrons as the other 2...

hope that helps

I partially agree with your answer. 😀

calcium ion is definitely smaller than chloride ion due to its larger number of protons.

However, Argon has tremendous radius because it's single atom gas. When the radius is measured, the only interaction between two atoms is the Van der Waals interaction, which makes the distance very large and the radius very large. While for other atoms, such as oxygen, the radius is measured by the distance between two oxygen atoms in O2 gas, where covalent presents, and therefore a smaller radius. So, nobel gas would have sufficiently larger radii and don't follow the "periodic rule".


I have check their actual radii, chloride (100 pm), chloride ion (181 pm), calcium (180 pm), calcium (100 pm), Argon (192 pm)


Thanks

 

[PooyaH]

I partially agree with your answer. 😀

calcium ion is definitely smaller than chloride ion due to its larger number of protons.

However, Argon has tremendous radius because it's single atom gas. When the radius is measured, the only interaction between two atoms is the Van der Waals interaction, which makes the distance very large and the radius very large. While for other atoms, such as oxygen, the radius is measured by the distance between two oxygen atoms in O2 gas, where covalent presents, and therefore a smaller radius. So, nobel gas would have sufficiently larger radii and don't follow the "periodic rule".


I have check their actual radii, chloride (100 pm), chloride ion (181 pm), calcium (180 pm), calcium (100 pm), Argon (192 pm)


Thanks

This is an example of Isoelectronic series, where you have the same number of electrons but different number of protons. REMEMBER...whichever has the highest number of protons would pull the electrons the tightest...thus, in this case calcium has the highest number of protons and will pull its electrons the tightest making its atomic radius smaller, Argon does the same and Cl- has the least number of protons and can't pull its electrons as tight as calcium and argon!!!

Hope it helps!

 

[ericyan3000]

This is an example of Isoelectronic series, where you have the same number of electrons but different number of protons. REMEMBER...whichever has the highest number of protons would pull the electrons the tightest...thus, in this case calcium has the highest number of protons and will pull its electrons the tightest making its atomic radius smaller, Argon does the same and Cl- has the least number of protons and can't pull its electrons as tight as calcium and argon!!!

Hope it helps!

shouldn't nobel gas be a special case and violate the rule?

 

[klutzy1987]

shouldn't nobel gas be a special case and violate the rule?

When all atoms/ions are in the same noble gas configuration, then you would just compare the ratio of protons to electrons. Whichever has the highest proton/electron ratio would have the smallest nucleus. Therefore Ca2+ has the smallest nucleus while Cl- has the largest nucleus.

 

[yakuza]

If you don't understand what they're trying to tell you, just think of it as cations --> get smaller from their parent element
anions --> get dramatically bigger from their parent element

 

[PooyaH]

shouldn't nobel gas be a special case and violate the rule?

As klutzy said, there's nothing special about nobel gases as far as atomic radius goes!!! All three have the same number of electrons and the same electron configuration...it's just the number of protons that would affect their atomic radius!