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.

Explanation

To predict the first ionization enthalpy (ΔiH°) value for aluminum (Al) and determine whether it is closer to 575 kJ mol⁻¹ or 760 kJ mol⁻¹, we can analyze the trends in ionization enthalpy across the third period elements.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
Ionization energy is the energy required to remove the outermost electron from a gaseous atom. It is influenced by two main factors: the effective nuclear charge (Z_eff) and the atomic size.

**Hint**: Remember that higher effective nuclear charge and smaller atomic size generally lead to higher ionization energy.
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