Which of the following electrons should have the highest value of ionisation energy (for the same value of the principal quantum number)?

The order of first ionization potentials of elements $Li, Be, B, Na$ is:

Which of the following elements has the lowest ionization energy?

In a group of elements,as the atomic number increases,which of the following is $NOT$ observed?

Which of the following represents the correct decreasing order of the first ionization enthalpy of $Ba, Sr, Ca,$ and $Mg$?

The first,second and third ionisation energies ($E_1, E_2$ and $E_3$) for an element are $7 \ eV$,$12.5 \ eV$ and $42.5 \ eV$ respectively. The most stable oxidation state of the element will be