Question

why gallium has smaller size than aluminum

Answer 1

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Even though Gallium lies belowAluminum, the atomic size of Gallium is smaller than Aluminum because of Shielding Effect. ... In case of Galliumthe outermost electrons are poorly shielded by d electrons increasing nuclear attraction of the outer electrons, which results the smaller radius of Gallium.


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Answer 2

Answer;

Gallium has smaller atomic radius than aluminium because the d orbital which is highly diffused offers poor shielding effect which results in increased nuclear charge. Due to increased charge by nucleus, outer electrons get attracted, decreasing the radius.