Answer
$F_{2}\lt Cl_{2}\lt Br_{2}\lt I_{2}$
Gases in order of increasing molar mass is
$F_{2}\lt Cl_{2}\lt Br_{2}\lt I_{2}$
Since entropy increases with the increase in molar mass, substances in order of increasing $S^{\circ}$ is
$F_{2}\lt Cl_{2}\lt Br_{2}\lt I_{2}$
Work Step by Step
Since all the substances given are diatomic gases, their molecular complexity and phase are same. Therefore, $S^{\circ}$ value is solely based on the molar mass.
Gases in order of increasing molar mass is
$F_{2}\lt Cl_{2}\lt Br_{2}\lt I_{2}$
Since entropy increases with the increase in molar mass, substances in order of increasing $S^{\circ}$ is
$F_{2}\lt Cl_{2}\lt Br_{2}\lt I_{2}$
