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Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory
All textbooksMcMurry 8th EditionCh.6 - Ionic Compounds: Periodic Trends and Bonding TheoryProblem 104
Chapter 6, Problem 104

Iron is commonly found as Fe, Fe2+, and Fe3+. (a) Write electron configurations for each of the three. (d) The third ionization energy of Ru is less than the third ionization energy of Fe. Explain.

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To write the electron configuration for Fe (neutral iron), first determine the number of electrons. Iron has an atomic number of 26, so it has 26 electrons. The electron configuration is written by filling the orbitals in the order of increasing energy: 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d⁶.
For Fe²⁺, remove two electrons from the neutral Fe configuration. Electrons are removed from the highest energy level first, which is the 4s orbital. Thus, the electron configuration for Fe²⁺ is: 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁶.
For Fe³⁺, remove one more electron from the Fe²⁺ configuration. The next electron is removed from the 3d orbital, resulting in the configuration: 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵.
To explain why the third ionization energy of Ru is less than that of Fe, consider the electron configurations and the stability of half-filled and fully filled subshells. Ru has a more stable electron configuration after losing three electrons compared to Fe, which makes it easier to remove the third electron from Ru.
Additionally, consider the effective nuclear charge and electron shielding. Ru has more protons than Fe, but the additional inner electrons provide more shielding, reducing the effective nuclear charge felt by the outer electrons, making it easier to remove the third electron.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For iron (Fe), the electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶. For the ions Fe²⁺ and Fe³⁺, electrons are removed from the outermost orbitals, resulting in configurations of 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ and 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵, respectively.
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Electron Configuration Example

Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion in its gaseous state. It generally increases with the atomic number due to increased nuclear charge, but can vary based on electron configuration and stability. The third ionization energy refers to the energy needed to remove the third electron, which can be influenced by the electron's proximity to the nucleus and the overall electron shielding effect.
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Comparison of Ionization Energies

When comparing the third ionization energies of different elements, factors such as atomic size, electron configuration, and effective nuclear charge play crucial roles. In the case of Ru and Fe, Ru has a higher atomic number and a more complex electron configuration, which can lead to a lower third ionization energy due to increased electron shielding and repulsion among electrons, making it easier to remove an electron compared to Fe.
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Related Practice
Textbook Question
Heating elemental cesium and platinum together for two days at 973 K gives a dark red ionic compound that is 57.67% Cs and 42.33% Pt. (c) What are the charge and electron configuration of the platinum ion?
Textbook Question
Consider the electronic structure of the element bismuth.(d) Would you expect element 115 to have an ionization ene-rgy greater than, equal to, or less than that of bismuth? Explain.
Textbook Question

Consider the electronic structure of the element bismuth. (a) The first ionization energy of bismuth is Ei1 = +703 kJ/ mol. What is the longest possible wavelength of light that could ionize an atom of bismuth?

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Textbook Question

Iron is commonly found as Fe, Fe2+, and Fe3+. (b) What are the n and l quantum numbers of the electron removed on going from Fe2+ to Fe3+?

Textbook Question

Iron is commonly found as Fe, Fe2++, and Fe3+. (c) The third ionization energy of Fe is Ei3 = +2952 kJ/mol. What is the longest wavelength of light that could ionize Fe2+(g) to Fe3+(g)?

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Textbook Question
The ionization energy of an atom can be measured by photo-electron spectroscopy, in which light of wavelength l is directed at an atom, causing an electron to be ejected. The kinetic energy of the ejected electron 1EK2 is measured by determining its velocity, v since EK = 1/2 mv2. The Ei is then calculated using the relationship that the energy of the inci-dent light equals the sum of Ei plus EK. (a) What is the ionization energy of rubidium atoms in kilo-joules per mole if light with l = 58.4 nm produces elec-trons with a velocity of 2.450 * 106m/s? (The mass of an electron is 9.109 * 10-31 kg.)