Arrange the following elements in increasing order of their first ionization enthalpy: Na , Mg , Al , Si , P Choose the correct answer from the options given below:

Step-by-step solution

The general trend of first ionization enthalpy increases across a period from left to right due to an increase in effective nuclear charge. However, exceptions occur due to extra stability of completely filled and half-filled orbitals. The electronic configurations of the given elements are: Na : [ Ne ] 3 s ¹ Mg : [ Ne ] 3 s ² Al : [ Ne ] 3 s ² 3 p ¹ Si : [ Ne ] 3 s ² 3 p ² P : [ Ne ] 3 s ² 3 p ³ Mg has a completely filled 3 s orbital, which is more stable and has greater penetration effect than the 3 p orbital of