The second ionisation energies are higher than the first ionisation energies. This is mainly due to the fact that after the removal of the first electrons, the atom changes inot mono valent position ion. In the ion, the number of electrons decreases but the nuclear charge remains the same. As a result of this, the remaining electrons are held more tightly by the nucleus and it becomes difficult to remove the second electron . Therefore, the value of second ionisation energy .`(IE_(2))` , is greater than that of the first ionisation energy `(IE_(1))` . Similarly third ionisation energy `(IE_(3))` is greater than that of second `IE_(2)`.
`IE_(1)` and `IE_(2)` of Mg metal are 178 and 348 kcal/mol respectively . The energy required for the given reaction is :`Mg(g)rarr Mg^(+2)(G)+2e^(-)`

Options

A. `+170` kcal/mol
B. `+526` kcal/mol
C. `-170` kcal/mol
D. `-526` kcal/mol

Answer

B