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Chapter 20: Problem 4

Without referring to the text, write the ground-state electron configurations of the first-row transition metals. Explain any irregularities.

Short Answer

Expert verified
The electron configurations of first-row transition metals are: Sc: \([Ar] 4s^2 3d^1\), Ti: \([Ar] 4s^2 3d^2\), V: \([Ar] 4s^2 3d^3\), Cr: \([Ar] 4s^1 3d^5\), Mn: \([Ar] 4s^2 3d^5\), Fe: \([Ar] 4s^2 3d^6\), Co: \([Ar] 4s^2 3d^7\), Ni: \([Ar] 4s^2 3d^8\), Cu: \([Ar] 4s^1 3d^{10}\), Zn: \([Ar] 4s^2 3d^{10}\). The irregularities observed for Cr and Cu, where an electron is moved from the \(4s\) orbital to the \(3d\) orbital, occur because the energy of the \(4s\) and \(3d\) orbitals are quite close and configurations where the \(d\) shell is half-filled or fully-filled are more energetically favorable.

Step by step solution

01

Determine the ground-state electron configuration

The ground-state electron configurations are based on the order of filling of the atomic orbitals. The order can be determined using the periodic table. The electron configurations of these elements are: Sc: \([Ar] 4s^2 3d^1\), Ti: \([Ar] 4s^2 3d^2\), V: \([Ar] 4s^2 3d^3\), Cr: \([Ar] 4s^1 3d^5\), Mn: \([Ar] 4s^2 3d^5\), Fe: \([Ar] 4s^2 3d^6\), Co: \([Ar] 4s^2 3d^7\), Ni: \([Ar] 4s^2 3d^8\), Cu: \([Ar] 4s^1 3d^{10}\), Zn: \([Ar] 4s^2 3d^{10}\).
02

Explain the irregularities

Two irregularities can be observed. One occurs for Chromium (Cr) and the other for Copper (Cu). For Chromium, rather than following the expected configuration of \([Ar] 4s^2 3d^4\), it's actually \([Ar] 4s^1 3d^5\). This is because the energy of the \(4s\) and \(3d\) orbitals are quite close and a configuration with more electrons in the \(3d\) orbital is more stable, especially when it results in a half-full \(d\) shell. In the case of Copper, we might expect \([Ar] 4s^2 3d^9\), but instead it is \([Ar] 4s^1 3d^{10}\). Moving one of the \(4s\) electrons to the \(3d\) shell again results in a more stable configuration because it results in a completely filled \(d\) shell.

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Most popular questions from this chapter

Compounds containing the \(\mathrm{Sc}^{3+}\) ion are colorless, whereas those containing the \(\mathrm{Ti}^{3+}\) ion are colored. Explain.

Write the formulas for each of these ions and compounds: (a) bis(ethylenediamine) dichlorochro\(\operatorname{mium}(\mathrm{III})\) (b) pentacarbonyliron(0), (c) potassium tetracyanocuprate(II), (d) tetraammineaquochlorocobalt(III) chloride.

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The \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\) complex is more labile than the \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}\) complex. Suggest an experiment that would prove that \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\) is a labile complex.
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