Atomic radius

[Jman247]

To decide atomic radius, how do I know when to use the trick to estimate based off charge vs when to calculate the Zeffective?

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[DAT Destroyer]

To decide atomic radius, how do I know when to use the trick to estimate based off charge vs when to calculate the Zeffective?

That depends on whether you are using atoms or ions.
If you are using atoms, go to the periodic table and look at the trends.
If you are going right and up, radius will decrease.
However, if you are using ions. Positive ions will always have radius and negative ions will have larger radius.

Hope this helps.

 

[Jman247]

So I can always use either trends or the trick for ions that negative is largest, and I don't have to calculate the Zeff?
when is it necessary to use Z-eff if there is the trick that negative anions are largest?

Thanks so much for the help!

 

[DAT Destroyer]

So I can always use either trends or the trick for ions that negative is largest, and I don't have to calculate the Zeff?
when is it necessary to use Z-eff if there is the trick that negative anions are largest?

Thanks so much for the help!

Zeff is necessary when you do not know the charge of the atom.
However, if you know the charge of the ions, then you can use those trends to figure out what is larger.
Hope this helps