Identify the number of electrons found in the outermost shell of a halogen atom.

Halogens belong to Group 17 of the periodic table (such as Fluorine, Chlorine, Bromine, Iodine). They have a general valence shell electronic configuration of $n{s}^{2}n{p}^5$, meaning they possess 7 electrons in their outermost shell and require 1 more electron to achieve a stable noble gas configuration.