Arranging the elements into different groups and periods in order of their increasing atomic numbers.
1 2 13 14 15
----- Be ---- ----- -----
Na Mg ---- Si P
We know, metallic character increases down a group and decreases along a period as we move from left to right. Therefore, Na is the most metallic element, followed by Mg and Si while P is the least metallic element. Comparing Be and Mg, Mg is more metallic than Be.
So, the overall order of increasing metallic character is:
P<Si<Be<Mg<Na