Which element has the higher shielding: chlorine or tin?

Chlorine.

Explanation:

Hello,

In this case, since electron shielding accounts for the atom's inner electrons capacity to shield its positively-charged nucleus from its valence electrons, when analyzing the rightwards periods in the periodic table, the shielding increases as a result of an increase in the number of electrons, causing an easier ionization of the valence electrons.

In such a way, since chlorine is located at the right of tin we can say it has more valence electrons and therefore a higher shielding.

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