[elfishies]

Hi, I am having troubles with this question. The answer that I got was Te, Sr2+, K, Se, Na+ but it was incorrect.
I know that the radius decreases across the period and increases as you go down the group.
it would be great if you could explain what I did wrong! Thank you

Select the lesser of each of the following pairs of radii:


 The covalent radius of Te
 The covalent radius of Sr

 The ionic radius of Sr2+
 The ionic radius of Rb+

 The metallic radius of K
 The metallic radius of Cs

 The covalent radius of Po
 The covalent radius of Se

 The ionic radius Mg2+
 The ionic radius of Na+

[mikasaur]

Why did you pick Na⁺?

[AdiDex]

can you tell me how we define the atomic radii ?? Is this due to Electronic configuration only ?? Or it has to something with the Nucleus also ??

[mikasaur]

can you tell me how we define the atomic radii ?? Is this due to Electronic configuration only ?? Or it has to something with the Nucleus also ??

Yes.

https://en.wikipedia.org/wiki/Atomic_radius

[Vidya]

can you tell me how we define the atomic radii ?? Is this due to Electronic configuration only ?? Or it has to something with the Nucleus also ??

It has many definitions : Covalent Radii ,Ionic Radii and Vander walls radii ...however in general in the periodic table if an atom has more number of shells then its radius is bigger (down the group) and along the period ..number of shells are same then nuclear charge becomes important ...more nuclear charge more attraction which results in shrinking of the atomic size and hence atomic radius.