* Smaller Size: Fluorine is smaller than bromine. This means the outermost electron in fluorine is closer to the nucleus, experiencing a stronger attractive force.
* Higher Effective Nuclear Charge: Fluorine has a higher effective nuclear charge (the positive charge felt by the outermost electron) than bromine. This is due to the smaller size and the increasing number of protons in the nucleus as you move down the halogen group.
Electron affinity is the change in energy when an electron is added to a neutral atom in the gaseous state. A more negative electron affinity indicates a greater tendency to gain an electron.
Therefore, fluorine's smaller size and higher effective nuclear charge result in a more negative electron affinity compared to bromine.
