$C{e^{ + 3}},\,\,L{a^{ + 3}},\,\,P{m^{ + 3}}\,\,$ and $Y{b^{ + 3}}\,\,$ have ionic radial in the increasing order as
$L{a^{ + 3}}\,\, < C{e^{ + 3}}\,\, < P{m^{ + 3}}\,\, < Y{b^{ + 3}}$
$Y{b^{ + 3}}\,\, < P{m^{ + 3}}\,\, < C{e^{ + 3}}\,<\,L{a^{ + 3}}$
$L{a^{ + 3}}\,\, = C{e^{ + 3}}\,\, < P{m^{ + 3}}\,\, < Y{b^{ + 3}}$
$Y{b^{ + 3}}\,\, < P{m^{ + 3}}\,\, < L{a^{ + 3}}\,\, < C{e^{ + 3}}$
