Question

why the metallic chracters increase from top to bottom in a group

Answer 1

Metallic Character is defined as tendency to loose electrons or to become electropositive

As we go down the group the valence electrons become more farther from nucleus and hence it is difficult for nucleus to hold outer electrons as size increase down the group so tendency to loose electrons increases down the group as a result mettalic character increases down the group

Answer 2

it is so because the losing capacity of that particular metallic character
increases top to bottom in a group. for example the group 15, nitrogen and phosphorus and non-metals arsenic and anti money are metalloids and Bismuth is a type of metal.