* Electron Configuration: A bromine atom has 35 electrons, while a bromide ion has 36 electrons. The extra electron in the bromide ion fills the outermost shell, increasing the electron-electron repulsion.
* Effective Nuclear Charge: The effective nuclear charge (the net positive charge experienced by an electron) is slightly lower for a bromide ion. This is because the extra electron in the bromide ion partially shields the other electrons from the nucleus.
* Shielding: The increased number of electrons in the bromide ion provides greater shielding, which means the outer electrons are less strongly attracted to the nucleus.
In summary: The extra electron in the bromide ion causes a greater electron-electron repulsion, a lower effective nuclear charge, and increased shielding, all of which contribute to a larger ionic radius compared to the atomic radius of bromine.
