<p>The five successive ionisation energies of an element are 800, 2427, 3658, 25024 and 32824 kJ&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>&nbsp;respectively. The number of valence electron is</p>