The basic nature of hydroxide of group  13 (group IIIA) decreases progressively down the group.

$14.534, 29.601, 47.448, 77.472, 97.888, 552.057, 667.029$

Find the number of valence shell electrons in that element.

Atomic mass, Covalent radius, Ionic radius $\left({\mathrm{X}}^{-}\right)$, Ionization energy, Electron affinity, Electronegativity, Hydration energy of uninegative ion $\left({\mathrm{X}}^{-}\right)$,

(a) Acidic strength $\Rightarrow \mathrm{ClOH}<\mathrm{BrOH}<\mathrm{IOH}$

(b) Basic strength $\Rightarrow \mathrm{MgO}<\mathrm{CaO}<\mathrm{SrO}<\mathrm{BeO}$

(c) Electronegativity $\Rightarrow \mathrm{Mg}<\mathrm{Na}<\mathrm{Si}<\mathrm{S}<\mathrm{Cl}$

(d) Electron affinity $\Rightarrow \mathrm{Mg}<\mathrm{Na}<\mathrm{Si}<\mathrm{S}<\mathrm{Cl}$

(e) $\%$ Ionic character $\Rightarrow \mathrm{NaF}<\mathrm{KF}<\mathrm{RbF}$

$\left(\mathrm{O}, \mathrm{S}\right), \left(\mathrm{He}, \mathrm{Ne}\right), \left(\mathrm{Kr}, \mathrm{Ne}\right), \left(\mathrm{Na}, {\mathrm{Na}}^{+}\right), \left(\mathrm{Cl}, {\mathrm{Cl}}^{-}\right), \left({\mathrm{I}}^{-}, {\mathrm{Cl}}^{-}\right), \left(\mathrm{Li}, \mathrm{Na}\right), \left({\mathrm{Li}}^{+}, {\mathrm{Na}}^{+}\right)$

${\mathrm{IE}}_1, {\mathrm{IE}}_2, {\mathrm{IE}}_3, {\mathrm{IE}}_4, {\mathrm{IE}}_5, {\mathrm{IE}}_6, {\mathrm{EGE}}_1, {\mathrm{EGE}}_2$

($\mathrm{IE}=$ ionization energy, $\mathrm{EGE}=$ electron gain enthalpy)