IP1 and IP2 of Mg are 178 and 348 k cal mol−1. The energy required for the reaction Mg → Mg2+ + 2e− is
526 kcal .
IP1 = 178 K cal mol−1
IP2 = 348 K cal mol−1
Now, take a look at the reaction
Mg → Mg2+ + 2e−
So, to take out two electrons from Mg, we have to provide energy.
Therefore, total energy required will be
= IP1 + IP2
= 178 + 348
= + 526 k. cal