Final answer:
Chlorine, with 17 electrons, has the electron configuration 1s²2s²2p⁶3s²3p⁵. Chlorine reacts with potassium bromide to form potassium chloride and bromine, as depicted in the balanced equation Cl2 + 2KBr → 2KCl + Br2. Iodine doesn't react with potassium bromide because it is less chemically active than chlorine.
Step-by-step explanation:
A neutral chlorine atom has 17 electrons. These electrons are distributed through the atomic orbitals in the following order: two electrons can occupy the 1s subshell, two in the 2s subshell, and six in the 2p subshell. This accounts for 10 electrons, which means there are seven more. Of those remaining seven, two fill the 3s subshell, and the last five occupy the 3p subshell. Therefore, the electron configuration for a chlorine atom is 1s²2s²2p⁶3s²3p⁵.
The reaction between chlorine and potassium bromide is represented by the balanced chemical equation Cl2 + 2KBr → 2KCl + Br2. Iodine does not react with potassium bromide because it is less reactive than chlorine, due to its position in the periodic table. Iodine is lower down in the halogen group, and its reactivity decreases as one moves down the group. Therefore, iodine does not have the chemical activity to displace bromine from potassium bromide.