The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuratio of the elements. The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpes generally increase and electron gain enthalpies become more negative across a period. In order words, the ionization enthalpy of the extreme left element in a period is the least and the electron gain enthalpy of the element on the extreme right is the highest negative. This results into high chemical reactivity at the two extremes and the lowest in the centre. Similary, down the group, the increase 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 reducing and oxidising behaviour, and also with metallic and non-metallic character respectively of the elements.
The correct order of the non-metallic character is:

Options

A. `B gt Al gt Mg gt K`
B. `Al gt Mg gt B gt K`
C. `Mg gt Al gt K gt B`
D. `K gt Mg gt Al gt B`

Answer

D