Which of the following groups of elements loses an electron most easily?

Which of the following is the incorrect order of ionisation energy $(I.E.)$?

In the photoelectric effect,if the work functions of $Li$,$Na$,and $Rb$ are $2.41 \ eV$,$2.30 \ eV$,and $2.09 \ eV$ respectively,the work function of $K$ could approximately be in $eV$?

The first three ionisation energies (in $kJ/mol$) of three representative elements are given below:

Element	$IE_1$	$IE_2$	$IE_3$
$P$	$495.8$	$4562$	$6910$
$Q$	$737.7$	$1451$	$7733$
$R$	$577.5$	$1817$	$2745$

Which of the following options is incorrect?

The successive ionization enthalpy values for an unknown element are $\Delta_i H_1 = 899 \ kJ/mol$,$\Delta_i H_2 = 1757 \ kJ/mol$,$\Delta_i H_3 = 14847 \ kJ/mol$,and $\Delta_i H_4 = 17948 \ kJ/mol$. To which group of the periodic table does this element belong?

Would you expect the first ionization enthalpies for two isotopes of the same element to be the same or different? Justify your answer.