• # question_answer The correct statement among the following is : A)  The alkali metals when strongly heated in oxygen form superoxide?s.B)  Caesium is used in photoelectric cells.C)  $NaHC{{O}_{3}}$ is more soluble in water than $KHC{{O}_{3}}$.D)  The size of hydrated ions of alkali metals increases from top to bottom,

$Li$ does not form peroxide or superoxide due to it small size. Solubility of carbonates and biocarbonates increases on moving down the group. The increasing order of size of hydrated ions of alkali metals is $L{{i}^{+}}>N{{a}^{+}}>{{K}^{+}}>R{{b}^{+}}>C{{s}^{+}}$ Cesium used in photoelectric cells due to its low I.E. Hence statements  is the only choice correct.