Respuesta :
Iodine has 7 valence electrons. It needs therefore only 1 electron to be stable this is why it is so reactive.
Answer: Iodine
Explanation: Cesium is the alkali metal which belongs to the group 1 of the periodic table.
Iodine is the Group 17 element which are known as the Halogens as they are the group of the most electronegative atoms.
Zinc belongs to the Transition metal d block .
Xenon belongs to the Group 18 of noble gases.
The electronic configuration will help us to determine which can gain electron to have a full outermost shell.
Cesium (Cs) = [Xe] 6s1
Zinc (Zn) = [Ar] 3d10 4s2
Iodine(I) = [Kr] 4d10 5s2 5p5
Xenon (Xe) = Kr 4d10 5s2 5p6
Thus Iodine can easily gain one electron to have complete outermost shell.
