The following table lists the first–ionization energies for two adjacent elements in…
CHEMISTRY · Subjective · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
The following table lists the first–ionization energies for two adjacent elements in Period 3.
Element First IE (kJ mol⁻¹)
Mg 738
Al 578
(a) Write the complete ground-state electron configuration for each element.
(b) The data show that the first-ionization energy of Al is lower than that of Mg, even though Al has a higher nuclear charge. Discuss how electron configuration, average electron–nucleus distance, and shielding together rationalize this deviation from the general periodic trend.
(c) Describe how a purely electrostatic model based on an inverse-square dependence on distance would predict the relative magnitudes of the forces acting on the outermost electrons of Mg and Al. Explain why this simple model alone cannot fully account for the experimental values given above.