Atomic radii consistently increase from B to Tl due to the increasing number of electron shells.

Ga has a significantly smaller radius than Al due to the lanthanide contraction.

Tl has a larger radius than In, but the increase is smaller than expected due to the d-block contraction.

While the general trend is an increase in radius down the group, Ga experiences a smaller than expected increase in radius compared to Al due to the poor shielding effect of the 3d electrons, while Tl exhibits a smaller than expected increase compared to In due to the poor shielding of both the 4f and 5d electrons.

$1.36,{\rm{ }}1.40,{\rm{ }}1.71$

$1.36,{\rm{ }}1.71,{\rm{ }}1.40$

$1.71,{\rm{ }}1.40,{\rm{ }}1.36$

$1.71,{\rm{ }}1.36,{\rm{ }}1.40$

${\rm{C}}{{\rm{l}}^ - }$

${{\rm{S}}^{2 - }}$

${\rm{N}}{{\rm{a}}^ + }$

${{\rm{F}}^ - }$

Increase in nuclear charge

Increase in the number of electron shells

Decrease in shielding effect

Increase in effective nuclear charge

${O^{ - 2}} > {F^ - } > F > O$

${F^ - } > {O^{2 - }} > O > F$

${O^{2 - }} > O > {F^ - } > F$

${O^{2 - }} > {F^ - } > O > F$

${\rm{Fe}} > F{{\rm{e}}^{2 + }} > F{{\rm{e}}^{3 + }}$

${{\rm{O}}^{2 - }} > {{\rm{O}}^ - } > {{\rm{O}}^ + }$

${{\rm{I}}^ - } > I > {{\rm{I}}^ + }$

All of these

$O > {O^ - } > {O^{2 - }}$

${O^ - } > {O^{2 - }} > O$

${O^{2 - }} > {O^ - } > O$

$O > {O^{2 - }} > {O^ - }$

$S^{2-} < Cl^- < Ar < K^+ < Ca^{2+}$

$Ca^{2+} < K^+ < Ar < Cl^- < S^{2-}$

$Ar < K^+ < Ca^{2+} < Cl^- < S^{2-}$

$K^+ < Ca^{2+} < Ar < S^{2-} < Cl^-$

$0.72,{\rm{ }}1.60$

${1.60,{\rm{ }}1.60}$

${0.72,{\rm{ }}0.72}$

${1.60,{\rm{ }}0.72}$

The increased shielding effect of d-electrons

The lanthanide contraction

The d-block contraction

Relativistic effects

Lithium (Li)

Beryllium (Be)

Boron (B)

Fluorine (F)