Why does metallic character decrease along a period?
On the other hand, as move across the Period, from left to right as we face it, the nuclear charge begins to exert its dominance, and tends to pull in on the valence electrons. Non-metals, on the right of the Periodic Table, tend to be reducing on the basis of the enhanced nuclear charge. The nuclear charge also results in the well-known decrease in atomic radii across the Period from left to right as we face it.
Given that the valence electrons are now strongly attracted to the nuclear charge, the element loses the metallic character of the transition and main group metals.