The correct increasing order of the magnitude of standard enthalpies of formation for group-1 halides is
NaI < NaBr < NaCl < NaF
Ion having highest hydration enthalpy among the given alkaline earth metal ions is:


In the first configuration (1) as shown in the figure, four identical charges \( q_0 \) are kept at the corners A, B, C and D of square of side length \( a \). In the second configuration (2), the same charges are shifted to mid points C, E, H, and F of the square. If \( K = \frac{1}{4\pi \epsilon_0} \), the difference between the potential energies of configuration (2) and (1) is given by: