Question

The first four ionisation energies of element are 580,640,1000,2700 K Cal/mol find the valance electron

Answer 1

3 valence electrons

Because,

energy different between 3 Rd and 4 th I.E. is much more higher than

1,2,3 ionisation energies

So, element can lose only 3 electrons in order to lose 4 th electron much more energy is required compared to other electrons so it can't lose 4 th electron

So valence electrons are 3

Hope it will help you