Textbook Question
Give the symbol of the element that has the (4.7)a. largest atomic size in Group 1A (1)
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9. Electrons in Atoms and the Periodic Table
Periodic Trend: Atomic Radius (Simplified)
Multiple Choice
In the ionic compound KBr, which ion has the larger ionic radius?
A
Cannot be determined without the bond length of KBr.
B
C
They are the same size because the compound is neutral.
D
Verified step by step guidance1
Identify the ions present in the compound KBr: potassium ion (K\(\textsuperscript{+}\)) and bromide ion (Br\(\textsuperscript{−}\)).
Recall that ionic radius depends on the charge and electron configuration of the ion. Cations (positive ions) generally have smaller radii than their neutral atoms because they lose electrons, reducing electron-electron repulsion.
Anions (negative ions) generally have larger radii than their neutral atoms because they gain electrons, increasing electron-electron repulsion and expanding the electron cloud.
Since K\(\textsuperscript{+}\) is a cation and Br\(\textsuperscript{−}\) is an anion, compare their ionic sizes based on their charges: the anion Br\(\textsuperscript{−}\) will have a larger ionic radius than the cation K\(\textsuperscript{+}\).
Therefore, without needing bond length data, the bromide ion (Br\(\textsuperscript{−}\)) has the larger ionic radius in KBr.
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