The first ionisation enthalpy `(Delta_(i)H^(o-))` values of the third period elements, `Na, Mg` and `Si` are respectively `496, 737` and `786 kJ mol^(-1)`. Predict whether the first `Delta_(i)H^(o-)` value for `Al` will be more close to `575` or `760 kJ mol^(-1)`? Justify your answer.