A line graph is described as follows: for the first eighteen elements
CHEMISTRY · Multi-part · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
A line graph is described as follows: for the first eighteen elements, the first-ionization energy (in kJ·mol⁻¹) is plotted on the y-axis versus atomic number on the x-axis. Local maxima occur at atomic numbers 2, 10, and 18, while pronounced minima appear at atomic numbers 3 and 11. Between each minimum and the following maximum, the curve rises steadily but with slight irregularities.
Answer the following questions regarding this representation of periodicity.
(a) Identify the chemical families that correspond to the three maxima and the two minima indicated on the graph.
(b) Explain, in terms of ground-state electron configurations, why elements located at the maxima exhibit substantially higher first-ionization energies than their immediate neighbors.
(c) The slope of the curve between atomic numbers 3 and 10 is steeper than the slope between atomic numbers 11 and 18. Describe how the effective nuclear charge Zeff changes across each of these two sections and relate that change to the differing slopes.