Trends in Ionic Sizes For each of these pairs, choose the smaller atom or ion: (a) A Cu atom or a Cu^2+ ion (b) A Se atom or a Se^2- ion (c) A Cu^+ ion or a Cu^2+ ion

Question

Trends in Ionic Sizes

For each of these pairs, choose the smaller atom or ion:
(a) A [latex]Cu[/latex] atom or a [latex]Cu^{2+}[/latex] ion
(b) A [latex]Se[/latex] atom or a [latex]Se^{2-}[/latex] ion
(c) A [latex]Cu^+[/latex] ion or a [latex]Cu^{2+}[/latex] ion

Accepted Answer

(a) [latex]Cu^{2+}[/latex] ion (b) [latex]Se[/latex] atom (c) [latex]Cu^{2+}[/latex] ion

Strategy and Explanation Consider the differences in the sizes of atoms and their corresponding ions based on electron loss or gain.
(a) A cation is smaller than its parent atom; therefore, [latex]Cu^{2+}[/latex] is smaller than a [latex]Cu[/latex] atom.
(b) Anions are larger than their parent atoms, so a [latex]Se^{2-}[/latex] ion is larger than a selenium atom.
(c) Both copper ions contain 26 protons, but [latex]Cu^{2+}[/latex] has one fewer electron than does [latex]Cu^+[/latex].
Correspondingly, the radius of [latex]Cu^{2+}[/latex] is smaller than that of [latex]Cu^+[/latex].

Chapter 7

Q. 7.PS.12

Q. 7.PS.12

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