Question

Orbital H atom He atom He+ ion 1s 2.18E-18 J 3.94E-18 J 8.72E-18 J 2p 0.545E-18 J 0.585E-18 J 2.18E-18 J Orbital H atom He atom He+ ion 1s 2.18E-18 J 3.94E-18 J 8.72E-18 J 2p 0.545E-18 J 0.585E-18 J 2.18E-18 J WhOrbital H atom He atom He+ ion 1s 2.18E-18 J 3.94E-18 J 8.72E-18 J 2p 0.545E-18 J 0.585E-18 J 2.18E-18 J which ionization energies show that stability of n = 1 orbitals increase with Z? H atom 1s and ? Which ionization energies show that an electron in a 1s orbital incompletely screens another electron in the same orbital? H atom 1s and?

Answer 1

The given values of ionization energies are as follows:

For H-atom (have only one electron in 1s orbital) = 2.18E-18 J

For He-atom (have only two electrons in 1s orbital) = 3.94E-18 J

For He⁺-ion (have only one electrons in 1s orbital) = 8.72E-18 J

The concept is that higher the ionization energy, higher the stability of the orbital. It means if ionization energy is high then the bounded electron in the orbital is more close to nucleus and cannot easily get removed from the system. It shows more energy requirement to remove the electron so the stability of that electron is higher but energy is lower. As the value of Z (number of protons in nucleus) increases the ionization energy for the same orbital increases.

Answer 1. As we move from H-atom (Z= 1) to He-atom (Z= 2) the ionizaion energy increased from 2.18E-18 J to 3.94E-18 J for n= 1 orbital. So these both ionization energies (2.18E-18 J and 3.94E-18 J) show that stability of n = 1 orbitals increase with Z.

Answer 2. Second condition is that where two electrons exist in same orbital. Here due to electron-electron repulsion one electron screens another one. Means it somewhat reduces nucleus attration force towards another electron. So ultimetaly with same value of Z, The value of ionization energies also depend on number of electrons in the orbital or epends on screening effect of electrons. This condition can be observed in H-atom (Z = 2 and electron = 2) and He+-ion (Z = 2 and electron = 1) . For the ion effective nuclear charge will be higher for single electron so attractive force is higher so ionization energy is also higher. This screening is less effective compare to screening by electrons present in higher levels. If we compare the energies of 2p orbitals of He-atom and He+-ion their is large difference compare to H-atom and He-atom 2p energies. It shows that by removal of one electron form H-atom the 1s and 2p orbitals are shifted more closed to nucleus and the screening effect is negligible compare to effective nucleus charge. So ionization energies of He-atom and He+ ion show that an electron in a 1s orbital incompletely screens another electron in the same orbital.