5.1 Factor Affecting Ionization Potential

  Periodic Table

• Number of shells: With the increase in the number of shells the atomic radius increases, i.e. the distance of outer most shell electron from the nucleus increases and hence the ionization potential decreases.
• Effective nuclear charge: Atomic size decreases with increase in effective nuclear charge because, higher the effective nuclear charge, stronger will be the attraction of the nucleus towards the electron of the outermost orbit and higher will be the ionization potential.
• Shielding effect: The electrons of internal orbit repel the electrons of the outermost orbit due to which the attraction of the nucleus towards the electron of the outermost orbit decreases and thus the atomic size increases and the value of the ionization potential decreases.
• Stability of half filled and fully filled orbital: The atoms whose orbitals are half filled $({p^3},{d^5}\:\& \:{f^7})$or fully filled $({s^2},{p^6},{d^{10}}\:\& \:{f^{14}})$ have greater stability than others, Therefore, they require greater energy for removing an electron. However, the stability of fully filled orbitals is greater than that of the half-filled orbitals.
• Penetration power: In any atom, the s orbital is nearer to the nucleus in comparison to p, d & f orbitals. Therefore, greater energy is required to remove an electron from s orbital than form p, d & f orbitals. Thus the decreasing order of ionization potential of s, p, d & f orbitals is as follows.$$s>p>d>f$$