Electronegativity values increase from left to right across a period in the periodic table because there is an increase in the charge of the nuclei in this direction.

First, let us define Electronegativity. Electronegativity is "the ability of an atom to attract electrons." In addition, electronegativity increases in elements from left to right, while on the other hand, electronegativity decreases from top to bottom in an element group. It decreases because the atomic radius increases as we go downward an element in the group.

It conforms what ever surface its in.