Total number of elements present in $5\mathrm{th}$ period of modern periodic table is

The successive ionization energies for element $\mathrm{X}$ is given below

${\mathrm{IE}}_1 : 250 \mathrm{kJ}{ \mathrm{mol}}^{-1}$

${\mathrm{IE}}_2 : 820 \mathrm{kJ}{ \mathrm{mol}}^{-1}$

${\mathrm{IE}}_3 : 1100 \mathrm{kJ}{ \mathrm{mol}}^{-1}$

${\mathrm{IE}}_4 : 1400 \mathrm{kJ}{ \mathrm{mol}}^{-1}$

Find out the number of valence electrons for the element $\mathrm{X}.$