We should observe where there is a jump in ionisation potential.In the question there is a jump at third step so no. of valence electrons is 3

To determine the number of electrons in the valence shell of an element based on its successive ionization potentials, we need to analyze the pattern and understand the concept of ionization energy.

Ionization energy is the energy required to remove an electron from an atom or ion. The successive ionization potentials represent the energy required to remove each electron from an atom one by one.

Given ionization potentials: 7.6 eV, 12.9 eV, 27 eV, and 92.5 eV

First Ionization Potential
The first ionization potential is the energy required to remove the first electron from an atom. In this case, the first ionization potential is 7.6 eV.

Second Ionization Potential
The second ionization potential is the energy required to remove the second electron from an atom after the first electron has been removed. Here, the second ionization potential is 12.9 eV.

Third Ionization Potential
The third ionization potential is the energy required to remove the third electron from an atom after the first two electrons have been removed. This value is given as 27 eV.

Fourth Ionization Potential
The fourth ionization potential is the energy required to remove the fourth electron from an atom after the first three electrons have been removed. The given value is 92.5 eV.

Analysis of Ionization Potentials
The ionization energy generally increases as we remove electrons from an atom because the remaining electrons experience stronger attraction from the positively charged nucleus. However, there are some exceptions when we consider the electronic configurations of elements.

Valence Electrons
Valence electrons are the electrons present in the outermost shell of an atom. They are responsible for the atom's chemical behavior and determine its valency.

Conclusion
Based on the given ionization potentials, we can conclude that the element has three electrons in its valence shell. This conclusion is drawn by analyzing the pattern of the ionization potentials and considering the general trends of ionization energy.