Electronegativity is a measure of the ability of an atom to attract electrons. The more electronegative an atom is, the more strongly it attracts electrons. Electronegativity increases from left to right across a period and decreases down a group.
Fluorine is in the top right corner of the periodic table, so it has the highest electronegativity of any element. Bromine is in the second row, so it has a lower electronegativity than fluorine.
The difference in electronegativity between fluorine and bromine is reflected in their ionization energies. The ionization energy is the energy required to remove an electron from an atom. The higher the ionization energy, the more difficult it is to remove an electron.
The ionization energy of fluorine is 1680 kJ/mol, while the ionization energy of bromine is 1140 kJ/mol. This difference in ionization energy shows that it is more difficult to remove an electron from fluorine than from bromine.
In summary, the higher electronegativity of fluorine makes it more difficult to remove an electron from fluorine than from bromine.
