The table provides ionic radii for two gaseous cations that are isoelectronic with neon
CHEMISTRY · Multi-part · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
The table provides ionic radii for two gaseous cations that are isoelectronic with neon.
Ion Charge Ionic radius / pm
Na⁺ +1 95
Mg²⁺ +2 65
Assume that, immediately before ionization, the outermost electron of each corresponding neutral atom is located at the same distance from the nucleus as the ionic radius listed. Use this information to analyze the relative strengths with which the nuclei of Na and Mg attract that electron.
(a) Using proportional reasoning, determine the ratio of the magnitude of the attractive electrostatic force exerted by the Mg nucleus on its outermost electron to that exerted by the Na nucleus on its outermost electron. Express your answer as a numerical multiplier (e.g., “the force for Mg is ___ times that for Na”).
(b) Based on your result in part (a), predict which atom has the higher first-ionization energy and justify your choice in terms of both nuclear charge and electron-to-nucleus distance.