CHEM 14A Chapter Notes - Chapter 1F.3: Isoelectronicity, Ionic Radius, Ionic Compound

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turquoisemoose666

2 Nov 2020

School

UCLA

Department

Chemistry and Biochemistry

Course

CHEM 14A

Professor

Dr.Laurence Lavelle

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Document Summary

The ionic radius is its share of the distance between neighboring ions in an ionic solid. The distance between the centers of a neighboring cation and anion is the sum of the two ionic radii. All cations are smaller than their parent atoms because the atom loses its valence electrons to form cation and exposes its core, which is generally much smaller than the parent atom. The radii of these ions increase down each group because the core electrons occupy shells with higher principal quantum numbers. The reason can be traced to the increased number of electrons in the valence shell of the anion and the repulsive effects exerted by electrons on one another. Anions and ions with the same number of electrons are called isoelectronic. Their radii differ because they have different nuclear charges. Ionization energy: the minimum energy needed to remove an electron from an atom in the gas phase.

Related Questions

In the ionic compounds LiF, NaCl, KBr, and RbI, the measured cationâanion distances are 2.01 AÌ (LiâF), 2.82 AÌ (Na-Cl), 3.30 AÌ (KâBr), and 3.67 AÌ (RbâI), respectively.

Predict the cation-anion distance of each ionic compound above using the values of ionic radii given in Figure 7.7 on page 257 in the textbook. To receive full credit, you must show how you predicted the distance for each molecule by providing a step-by-step solution for each molecule. The solution for each molecule is worth 8 points; thus, a total of 32 total points is possible for this question.

Chemistry Multiple Choice Questions (1,2,3)

Ionic Radii

The size of ions as measured by ionic radii varies in a systematic manner. The size of the ion can be explained in part by effective nuclear charge, Zeff, which is the net nuclear charge felt by an electron. The effective nuclear charge takes into account the actual nuclear charge and the shielding of this charge by inner electrons. When an atom loses electrons, the resulting cation is smaller both because the remaining electrons experience a larger Zeff and because these electrons are usually in orbitals closer to the nucleus than the electrons that were lost. The more electrons that are lost, the smaller the ion becomes.

Similarly, when an atom gains electrons, the resulting anion is larger owing to both increased electron-electron repulsions and a reduction in Zeff. The more electrons that are gained, the larger the ion becomes.

Part A

Rank the following ions in order of decreasing radius: O2â,S2â,Se2â,Te2â, and Po2â. Use the periodic table as necessary.

Rank from largest to smallest radius. To rank items as equivalent, overlap them.

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Part B

Rank the following items in order of decreasing radius: Na, Na+, and Naâ.

Rank from largest to smallest radius. To rank items as equivalent, overlap them.

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Part C

The following ions contain the same number of electrons. Rank them in order of decreasing ionic radii.

Rank from largest to smallest radius. To rank items as equivalent, overlap them.

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CHEM 14A Chapter Notes - Chapter 1F.3: Isoelectronicity, Ionic Radius, Ionic Compound

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