The number of alkali metal(s), from Li, K, Cs, $Rb$ having ionization enthalpy greater than $400\, kJ$ $mol ^{-1}$ and forming stable super oxide is
K and Rb form stable superoxides, but Cs has an ionization enthalpy less than 400 kJ/mol.
Thus, the correct answer is 2, as K and Rb are the metals that meet the criteria.
A square loop of sides \( a = 1 \, {m} \) is held normally in front of a point charge \( q = 1 \, {C} \). The flux of the electric field through the shaded region is \( \frac{5}{p} \times \frac{1}{\varepsilon_0} \, {Nm}^2/{C} \), where the value of \( p \) is: