Answer:
Rb
Explanation:
Second ionization energy is the energy required for the removal of the second loosely bonded valence electron from an isolated gaseous atom.
The given elements:
Rb , Sr, Y and Zr
These are the elements of the fifth period.
The electronic configuration of Rb - [tex][Kr]5s^1[/tex]
The electronic configuration of Sr - [tex][Kr]5s^2[/tex]
The electronic configuration of Y - [tex][Kr]5s^24d^1[/tex]
The electronic configuration of Zr - [tex][Kr]5s^24d^2[/tex]
When one electron is removed from Rb, the cation attains the noble gas configuration due to which the removal of second electron from Rb is very very difficult. Thus, Rb has the largest second ionization energy.
The values of the second ionization of these elements are:
Rb = 2633 kJ/mol
Sr = 1064.2 kJ/mol
Y = 1180 kJ/mol
Zr = 1270 kJ/mol
