Use the valence molecular orbital configuration to determine which of the following species is expected to have the lowest ionization energy: (a) \(\mathrm{C}_{2}^{+} ;\) (b) \(\mathrm{C}_{2}\) (c) \(\mathrm{C}_{2}^{-}\)

Short Answer

Expert verified
The species \(C_{2}^{-}\) is expected to have the lowest ionization energy.

Step by step solution

01

Understand the Molecular Ion Notations

The notation of a molecule in the form \(C_{2}^{+}\) or \(C_{2}^{-}\) represents a molecular ion where \(C_{2}^{+}\) has lost an electron and \(C_{2}^{-}\) has gained an electron. ⁠Subsequently, \(C_{2}\) is a neutral molecule with no charge.
02

Determine the Valence Molecular Orbital Configuration for Each Species

The valence molecular orbital configuration for each species is as follows: For \(C_{2}^{+}\), the highest energy electron resides in the \(\pi\) antibonding orbital; For \(C_{2}\), the highest energy electron is in the \(\pi\) orbital;For \(C_{2}^{-}\), the highest energy electron is in the \(\pi^{*}\) antibonding orbital. The asterisk indicates a higher energy antibonding orbital.
03

Compare Ionization Energies Based on Valence Molecular Orbital Configurations

Ionization energy increases with the energy of the most loosely bound electron. Hence, \(C_{2}^{-}\) has the lowest ionization energy because the highest energy electron lies in the \(\pi^{*}\) antibonding orbital, which is a higher energy level compared to the \(\pi\) orbital or \(\pi\) antibonding level. Removing an electron from the \(\pi^{*}\) antibonding orbital would require less energy than removing one from the \(\pi\) or \(\pi\) antibonding orbital.

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