The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuration of the elements.
The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpies generally increase and electron gain enthalpies become more negative across a period. In other words, the ionization enthalpy of the exterme left element in a period is the least and teh electron gain enthalpy of the element on the exterme right is the highest negative. This results into high chemical reactivity at the two extermes and the lowest in he centre. Similarly down the group, the increase in atomic and ionic radii result in gradual decrease in ionization enthalpies and a regular decrease (with exception in some third period elements) in electron gain enthalpies in the case of main group elements.
The loss and gain of electrons can be co-related with the reducting and oxidising behaviour, and also with metallic and non-metallic character respectively, of the elements.
The correct order of the metallic character is:

Options

A. `AI gt Mg gt Na gt Si`
B. `Na gt Mg lt Al gt Si`
C. `Na gt Mg gt Al gt Si`
D. `AI gt Mg gt Si gt Na`

Answer

C

Explanation

The metallic character of the elements is highest at the extremely left (low ionisation energies) and then decreases across the period from left to right (ionisation energies increases across the period).