Two hypothetical graphs are verbally described below
CHEMISTRY · Multi-part · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
Two hypothetical graphs are verbally described below. Each graph plots first-ionization energy versus atomic number over one complete period.
• Graph P: Covers atomic numbers 11 through 18. The lowest point is at 11, followed by a gradual rise with a small dip at 13, then a larger peak at 18.
• Graph Q: Covers atomic numbers 19 through 26. The curve again begins with a minimum at 19, but rises less steeply; after 21, the plotted values increase only slightly, creating a plateau that persists through 24 before a moderate rise leads to a peak at 26.
Answer the following questions about these descriptions.
(1) Part 1: (a) For each graph, identify the block (s, p, or d) to which the majority of the elements plotted belong. Support your answer with reference to periodic table structure.
(2) Part 2: (b) Explain why the increase in IE1 across Graph Q is less pronounced than that across Graph P, even though both graphs span eight consecutive elements.
(3) Part 3: (c) In Graph Q, predict whether a noticeable dip analogous to the one at Z=13 in Graph P would occur, and specify the atomic number at which it is most likely. Justify your reasoning in terms of subshell electron configurations and exchange stabilization.
(4) Part 4: (d) Suppose both graphs were extended one element beyond the ranges described. For each graph, state whether you would expect the next plotted point to be higher or lower than the preceding one, and explain your expectation with reference to periodic trends.