Dear student
In the periodic table ,
As we go from left to right the metallic character decreases and the non metallic character increases. Because as we move from left to right in a period, the number of valence electrons increases by one at each succeeding element but the number of shells remains same.
Due to this effective nuclear charge increase. More is the effective nuclear charge, more is the attraction between nuclei and electron. Hence, the tendency of the element to lose electrons decreases, this result in decrease in metallic character. Furthermore, the tendency of an element to gain electrons increases with increases in effective nuclear charge, so non-metallic character increases on moving from left to right in a period.

Hi Gopal,

As we move from left to right in the periodic table, the valence electrons keeps increasing by one at each of the succeeding element. Here, the number of shells does not change. This causes nuclear charge to increase which also increases attractive force between nuclei and electrons. This in turn decreases the tendency to lose electrons which decreases the metallic character. As we keep moving forward, the tendency to gain electrons increases which increases the non-metallic character of the elements as we move from left to right in a periodic table.