Arrange the elements in decreasing order of first ionization energy.

Rank from highest to lowest first ionization energy. To rank items as equivalent, overlap them.

In, Ge, Se, Cs

PART B:

Arrange the elements in order of decreasing first ionization energy. Rank from highest to lowest first ionization energy. To rank items as equivalent, overlap them.

element x (radius (pm) : 110)

element y (radius (pm) : 199)

element z (radius (pm) : 257)

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.

In the periodic table, down the group, as atomic radius of elements increases, the ionization energy decreases

Whereas, across a period, as atomic radius of elements decreases, the ionization energy increases.

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

Therefore, the decreasing order of first ionization energy: Se > Ge > In > Cs

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

Therefore, the decreasing order of first ionization energy: x > y > z