The table below lists experimentally measured ionic radii for six species that all…
CHEMISTRY · Multi-part · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
The table below lists experimentally measured ionic radii for six species that all possess ten electrons.
Ion
Nuclear Charge, Z
Ionic Radius (pm)
O^{2−}
8
140
F^{−}
9
133
Ne
10
112
Na^{+}
11
95
Mg^{2+}
12
65
Al^{3+}
13
50
Throughout this question, treat the numerical values as exact.
(a) For each consecutive pair of ions in the table, calculate the percent decrease in ionic radius when the nuclear charge increases by one. Show your calculations for all five intervals.
(b) If ionic radius is plotted on the vertical axis and nuclear charge on the horizontal axis, describe in words the qualitative shape and slope of the resulting graph. Your description should include any regions where the rate of decrease appears to change noticeably.
(c) Provide a chemical explanation for the overall trend in ionic radius across the series. In your answer, make explicit reference to both the number of electrons present and the magnitude of the nuclear charge.
(d) Based on the pattern you observe, estimate a reasonable ionic radius for Si^{4+}. Justify your estimate quantitatively and qualitatively.