Textbook Question
For each set of atoms and ions, pick the smallest one.
a. I, I+, I−
b. Be2+, Ca2+, Mg2+
c. Fe, Fe2+, Fe3+
10. Periodic Properties of the Elements
Periodic Trend: Ionic Radius
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Which of the following atoms or ions is the largest?
A
O2−
B
F−
C
Ne
D
Na+
E
Mg2+
Verified step by step guidance1
Understand that atomic and ionic sizes are influenced by the number of electrons and the effective nuclear charge. Generally, anions are larger than their neutral atoms, and cations are smaller.
Consider the electron configuration of each species: O2−, F−, Ne, Na+, and Mg2+. Determine the number of electrons in each species.
Recognize that O2− has gained electrons compared to a neutral oxygen atom, increasing electron-electron repulsion and resulting in a larger size.
Compare the effective nuclear charge experienced by the electrons in each species. A higher effective nuclear charge pulls electrons closer to the nucleus, reducing size.
Arrange the species in order of increasing size based on the number of electrons and effective nuclear charge, identifying which species is the largest.
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