The correct order of electronegativity for given elements is

On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group. As a result, the most electronegative elements are found on the top right of the periodic table, while the least electronegative elements are found on the bottom left.

Element             Electronegativity

P                         $2.1$

C                           $2.5$

Br                          $3.0$                   

At                           $2.2$

Hence, the correct order is Br > C > At > P.