Question

In the conversion of \(\mathrm{N}_{2}\) to \(\mathrm{N}_{2}^{+}\) ion the electron is removed from (1) \(\sigma\) orbital (2) \(\sigma^{*}\) orbital (3) \(\pi\) orbital (4) \(\pi^{*}\) orbital

Short answer

In the conversion of \(\text{N}_{2}\) to \(\text{N}_{2}^{+}\), the electron is removed from the \(\sigma\) orbital.

Step-by-step solution

Understand the question

The question asks from which orbital an electron is removed during the conversion of \(\text{N}_{2}\) to \(\text{N}_{2}^{+}\). This involves understanding the molecular orbitals of \(\text{N}_{2}\).

Determine the electron configuration of N2

The molecular orbitals for \(\text{N}_{2}\) can be described as follows: \(\text{N}_{2} : \sigma_{1s}^{2} \sigma_{1s}^{*2} \sigma_{2s}^{2} \sigma_{2s}^{*2} \pi_{2p}^{4} \sigma_{2p}^{2}\). The last electrons go into the \(\pi_{2p}\) and \(\sigma_{2p}\) orbitals, with \(\pi_{2p}\) being higher in energy.

Identify the highest occupied molecular orbital (HOMO)

For \(\text{N}_{2}\), the HOMO is the \(\sigma_{2p}\) orbital because it is fully occupied and highest in energy amongst the occupied orbitals.

Determine from which orbital electron is removed

When \(\text{N}_{2}\) is ionized to form \(\text{N}_{2}^{+}\), an electron will be removed from the HOMO, which is the \(\sigma_{2p}\) orbital.

Match to given options

Among the given options, the \(\sigma\) orbital matches the \(\sigma_{2p}\) orbital from which the electron is removed.

Key concepts

Nitrogen molecule

The nitrogen molecule, represented as \( \text{N}_2 \), is composed of two nitrogen atoms. Nitrogen atoms have the atomic number 7, so each atom provides 5 valence electrons to the bond. Nitrogen molecules are diatomic molecules, meaning they exist in pairs. These molecules form incredibly strong triple bonds, making them quite stable.
In molecular orbital theory, we combine atomic orbitals from each nitrogen atom to form molecular orbitals. These molecular orbitals are either bonding or antibonding, affecting the stability of the molecule.
For \( \text{N}_2 \), the molecular orbital configuration is as follows:
\[ \text{N}_2: \sigma_{1s}^{2} \sigma_{1s}^{*2} \sigma_{2s}^{2} \sigma_{2s}^{*2} \pi_{2p}^{4} \sigma_{2p}^{2} \]
Each orbital can hold a specific number of electrons, with bonding orbitals filling first and being lower in energy than antibonding orbitals.

Ionization

Ionization is the process of removing or adding an electron to an atom or molecule. For diatomic nitrogen, ionizing it means removing an electron and converting \( \text{N}_2 \) into \( \text{N}_2^+ \).
To understand ionization, we need to know from which molecular orbital this electron is removed. Upon removal, the molecular orbitals are rearranged as a result of the resulting electron configuration.
For the nitrogen molecule, the electron configuration shows that the highest occupied energy level is \( \sigma_{2p} \) orbital—the highest among all filled molecular orbitals. Ionization thus involves removing an electron from this specific orbital.

Highest occupied molecular orbital (HOMO)

The Highest Occupied Molecular Orbital (HOMO) is the molecular orbital that contains the highest energy electrons. In the case of \( \text{N}_2 \), this is the \( \sigma_{2p} \) orbital.
When discussing molecular orbitals, it's crucial to consider both bonding and antibonding orbitals. Bonding orbitals help stabilize the molecule, while antibonding orbitals reduce its stability.
The unique aspect of the HOMO is that it is the reference point during ionization. By removing an electron from the HOMO (in this case, the \( \sigma_{2p} \) orbital), we can predict the resulting ion's stability and properties. This is because removing an electron from the HOMO translates directly to a change in the molecule's electronic configuration and energy state.
The understanding of HOMO is essential in chemistry as it greatly affects how molecules interact with each other and how they react in chemical reactions.