Nuclear Charge, Generally due to increase in nuclear charge, electrostatic force of attraction increases, The first risc ionization energies of an element E are as follows:

 3)        Nuclear Charge:

             Generally due to increase in nuclear charge, electrostatic force of attraction increases between protons and electrons as a result I.E increases. But only simply increase in number of protons or increased in nuclear charge is not significant. Actually effective or net nuclear charge is important e.g; In case of lithium its nuclear charge is +3, as there protons are present in the nucleus but two protons are screened two electrons present in the first shell, hence only+1 charge has effect on valance electron. Thus total nuclear charge in lithium is +3 but net or effective nuclear charge is +1. This effective nuclear charge increases across the period because no of protons increase in the nucleus but no of electrons increases in the same shell hence shielding or screwing effect remains constant.

Q.         The first risc ionization energies  of an element E are as follows:

             578 (first), 1817, 2745, 11578, 14831, 18378 KJ mole^-1.

Answer:

                       There is a sudden jump in I.E when the fourth electron is removed. This shows that fourth electron is present in air inner shell and it valence shell contains there electrons because there is  less difference in first three successive ionization energies. Thus element E is from Group III of the periodic table.

 TRENDS IN IONISATION ENERGIES ACROSS THE PERIOD:

             There is a general increase in first ionization energy as we move across the period of the periodic table. This increase is due to increase in net nuclear. Across the period number pf shells remains the same. Hence with the addition of every new proton in the nucleus new electrons are added up in the same shell. A a result screening effect remains unchanged and effective or net nuclear charge increases. Due to this reason nucleus gets more strong hold on the valence electrons when we mole from left to right in a period, atomic radius (size) decreases across the period and values of ionization energies increases across the period.

             Overall, there is a general increases in first ionization energy as we move across the period of the periodic table. This increase is due to an increase in effective (net) nuclear charge e.g.