Answer:
The decreasing order of first ionization energy: Se > Ge > In > Cs
The decreasing order of first ionization energy: x > y > z
Explanation:
Ionization energy refers to the energy needed to completely pull out an electron from the valence shell of a neutral gaseous atom.
First ionization energy is the energy involved in the removal of first valence electron.
<u><em>In the periodic table, down the group, as atomic radius of elements increases, the ionization energy decreases </em></u>
<u><em>Whereas, across a period, as atomic radius of elements decreases, the ionization energy increases.</em></u>
PART (A):
Position of the given elements in the periodic table:
Indium (In): Group 13, period 5
Germanium (Ge): Group 14, period 4
Selenium (Se): Group 16, period 4
Caesium (Cs): Group 1, period 6
Thus, the increasing order of atomic radius: Se < Ge < In < Cs
<u>Therefore, the decreasing order of first ionization energy: </u><u>Se > Ge > In > Cs</u>
PART (B):
Given elements:
element x: radius = 110 pm
element y: radius = 199 pm
element z: radius = 257 pm
Thus, the increasing order of atomic radius: x < y < z
<u>Therefore, the decreasing order of first ionization energy:</u><u> x > y > z</u>
