Answer:
At < I < Br < Cl < F
Explanation:
Electronegativity is defined as the ability of an atom to attract pair of electrons. On the periodic table, electronegativity decreases down the group and increases along the period.
The given atoms belong to the same group, so following the above rule, F has the highest electronegativity than other given atoms as it is at the top of the group and At will have the least electronegativity as it is at the bottom of the group.
Hence, the order of increasing electronegativity is
At < I < Br < Cl < F.
