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Chapter 7: Problem 93

In the chemical process called electron transfer, an electron is transferred from one atom or molecule to another. (We will talk about electron transfer extensively in Chapter 20.) A simple electron transfer reaction is $$\mathrm{A}(g)+\mathrm{A}(g) \longrightarrow \mathrm{A}^{+}(g)+\mathrm{A}^{-}(g)$$ In terms of the ionization energy and electron afnity of atom A, what is the energy change for this reaction? For a representative nonmetal such as chlorine, is this process exothermic? For a representative metal such as sodium, is this process exothermic?

Short Answer

Expert verified
The energy change (ΔE) for an electron transfer reaction can be calculated using the formula: ΔE = Electron affinity (EA) - Ionization energy (IE). For chlorine, a representative nonmetal, ΔE = \(-1600.2 \,kJ/mol\), and for sodium, a representative metal, ΔE = \(-548.8 \,kJ/mol\). Since both energy changes are negative, the electron transfer process is exothermic for both chlorine and sodium, meaning it releases energy.

Step by step solution

01

Write the energy change formula for electron transfer

To calculate the energy change for this electron transfer reaction, we can use the following equation: Energy change (ΔE) = Electron affinity (EA) - Ionization energy (IE)
02

Determine the Ionization Energy and Electron Affinity of Chlorine

For a representative nonmetal such as chlorine, we need to find the IE and EA values. The values from the literature are: IE (Chlorine) = \(1251.2 \,kJ/mol\) EA (Chlorine) = \(-349 \,kJ/mol\)
03

Calculate the Energy Change for Chlorine

Now, we can calculate the energy change for the electron transfer reaction involving chlorine using the formula from Step 1: ΔE (Chlorine) = EA (Chlorine) - IE (Chlorine) ΔE (Chlorine) = \(-349 \,kJ/mol\) - \(1251.2 \,kJ/mol\) ΔE (Chlorine) = \(-1600.2 \,kJ/mol\)
04

Determine if the Electron Transfer is Exothermic for Chlorine

Since the energy change (ΔE) for chlorine is negative, the process is exothermic for chlorine (releases energy).
05

Determine the Ionization Energy and Electron Affinity of Sodium

For a representative metal such as sodium, we need to find the IE and EA values. The values from the literature are: IE (Sodium) = \(495.8 \,kJ/mol\) EA (Sodium) = \(-53 \,kJ/mol\)
06

Calculate the Energy Change for Sodium

Now, we can calculate the energy change for the electron transfer reaction involving sodium using the formula from Step 1: ΔE (Sodium) = EA (Sodium) - IE (Sodium) ΔE (Sodium) = \(-53 \,kJ/mol\) - \(495.8 \,kJ/mol\) ΔE (Sodium) = \(-548.8 \,kJ/mol\)
07

Determine if the Electron Transfer is Exothermic for Sodium

Since the energy change (ΔE) for sodium is negative, the process is exothermic for sodium (releases energy). In conclusion, the electron transfer process is exothermic for both the nonmetal chlorine and the metal sodium.

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Most popular questions from this chapter

Consider the first ionization energy of neon and the electron affinity of fluorine. (a) Write equations, including electron configurations, for each process. (b) These two quantities have opposite signs. Which will be positive, and which will be negative? (c) Would you expect the magnitudes of these two quantities to be equal? If not, which one would you expect to be larger?

Hydrogen is an unusual element because it behaves in some ways like the alkali metal elements and in other ways like nonmetals. Its properties can be explained in part by its electron configuration and by the values for its ionization energy and electron affinity. (a) Explain why the electron affinity of hydrogen is much closer to the values for the alkali elements than for the halogens. (b) Is the following statement true? "Hydrogen has the smallest bonding atomic radius of any element that forms chemical compounds." If not, correct it. If it is, explain in terms of electron configurations. (c) Explain why the ionization energy of hydrogen is closer to the values for the halogens than for the alkali metals. (d) The hydride ion is \(\mathrm{H}^{-} .\) Write out the process corresponding to the first ionization energy of the hydride ion. (e) How does the process in part (d) compare to the process for the electron affinity of a neutral hydrogen atom?

We will see in Chapter 12 that semiconductors are materials that conduct electricity better than nonmetals but not as well as metals. The only two elements in the periodic table that are technologically useful semiconductors are silicon and germanium. Integrated circuits in computer chips today are based on silicon. Compound semiconductors are also used in the electronics industry. Examples are gallium arsenide, GaAs; gallium phosphide, GaP; cadmium sulfide, CdS; and cadmium selenide, CdSe. (a) What is the relationship between the compound semiconductors’ compositions and the positions of their elements on the periodic table relative to Si and Ge? (b) Workers in the semiconductor industry refer to "II–VI" and "III–V" materials, using Roman numerals. Can you identify which compound semiconductors are II–VI and which are III–V? (c) Suggest other compositions of compound semiconductors based on the positions of their elements in the periodic table.

(a) Which ion is smaller, \(\mathrm{Co}^{3+}\) or \(\mathrm{Co}^{4+} ?(\mathbf{b})\) In a lithium-ion battery that is discharging to power a device, for every \(\mathrm{Li}^{+}\) that inserts into the lithium cobalt oxide electrode, a \(\mathrm{Co}^{4+}\) ion must be reduced to a \(\mathrm{Co}^{3+}\) ion to balance charge. Using the CRC Handbook of Chemistry and Physics or other standard reference, find the ionic radii of \(\mathrm{Li}^{+}, \mathrm{Co}^{3+},\) and \(\mathrm{Co}^{4+} .\) Order these ions from smallest to largest. (c) Will the lithium cobalt oxide cathode expand or contract as lithium ions are inserted? (d) Lithium is not nearly as abundant as sodium. If sodium ion batteries were developed that function in the same manner as lithium ion batteries, do you think "sodium cobalt oxide" would still work as the electrode material? Explain. (e) If you don’t think cobalt would work as the redox-active partner ion in the sodium version of the electrode, suggest an alternative metal ion and explain your reasoning.

You read the following statement about two elements \(\mathrm{X}\) and \(\mathrm{Y} :\) One of the elements is a good conductor of electricity, and the other is a semiconductor. Experiments show that the first ionization energy of \(\mathrm{X}\) is twice as great as that of Y. Which element has the greater metallic character?
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