Question

The hybridization of atomic orbitals of nitrogen \(\mathrm{inNO}_{2}^{+}, \mathrm{NO}_{3}^{-}\) and \(\mathrm{NH}_{4}^{+}\) are: (a) \(\mathrm{sp}^{2}, \mathrm{sp}^{3}\) and \(\mathrm{sp}^{2}\) respectively (b) sp, sp and sp respectively (c) \(\mathrm{sp}^{2}\), sp and sp \(^{3}\) respectively (d) \(\mathrm{sp}^{2}, \mathrm{sp}^{3}\) and sp respectively

Short answer

The correct option is (c) \(\mathrm{sp}, \mathrm{sp}^{2}, \mathrm{sp}^{3}\) respectively.

Step-by-step solution

Determine hybridization of NO2+

First, consider the ion \(\mathrm{NO}_{2}^{+}\). The nitrogen atom is bonded to two oxygen atoms and has no lone pairs, given the positive charge. The steric number, which is the sum of bonded atoms and lone pairs around the nitrogen, is 2. According to VSEPR theory, a steric number of 2 corresponds to \(\mathrm{sp}\) hybridization. Thus, the hybridization of nitrogen in \(\mathrm{NO}_{2}^{+}\) is \(\mathrm{sp}\) hybridization.

Determine hybridization of NO3-

Next, consider the ion \(\mathrm{NO}_{3}^{-}\). The nitrogen atom is bonded to three oxygen atoms and has no lone pairs due to the negative charge balancing with the bonded oxygen atoms. The steric number is 3. According to VSEPR theory, a steric number of 3 corresponds to \(\mathrm{sp}^{2}\) hybridization. Therefore, the nitrogen in \(\mathrm{NO}_{3}^{-}\) is \(\mathrm{sp}^{2}\) hybridized.

Determine hybridization of NH4+

Finally, consider the ion \(\mathrm{NH}_{4}^{+}\). The nitrogen atom is bonded to four hydrogen atoms and has no lone pairs. The steric number is 4. This corresponds to \(\mathrm{sp}^{3}\) hybridization according to VSEPR theory. Thus, the nitrogen in \(\mathrm{NH}_{4}^{+}\) is \(\mathrm{sp}^{3}\) hybridized.

Key concepts

Nitrogen Compounds

Nitrogen is found in various chemical compounds, exhibiting different bonding characteristics. These are known as nitrogen compounds, and they often include well-known ions like

• NO₂⁺
• NO₃^-
• NH₄⁺

In these ions, nitrogen forms bonds with other atoms such as oxygen or hydrogen. The bonding and shape of these nitrogen compounds are influenced by the hybridization of nitrogen's atomic orbitals. Hybridization is a key concept here. It determines how nitrogen's atomic orbitals, usually in energy levels 2s and 2p, mix and form hybrid orbitals. These hybrid orbitals help in understanding the molecular geometry and stability of the compound.

VSEPR Theory

The Valence Shell Electron Pair Repulsion (VSEPR) theory is essential for predicting the shapes of molecules. According to VSEPR theory, electron pairs around a central atom arrange themselves to minimize repulsion, which molds the shape of the molecule. Because nitrogen commonly has multiple bonds, VSEPR theory helps predict the hybridization required for bonding. For example:

• If nitrogen bonds with only two other atoms, such as in NO₂⁺, the steric number is 2, matching with sp hybridization.
• In NO₃^-, nitrogen is bonded to three oxygen atoms, leading to a steric number of 3 and thus sp² hybridization.
• NH₄⁺, with nitrogen bonded to four hydrogens, has a steric number of 4, resulting in sp³ hybridization.

The theory helps ensure that the molecule's electron cloud is distributed optimally around the center, allowing us to predict and understand the 3D shapes of molecules.

Molecular Geometry

Molecular geometry defines the three-dimensional shape of a molecule, influenced by the arrangement of electron pairs around the central atom. For nitrogen compounds, this geometry is critical. The shape of a molecule can affect everything from physical properties to reactivity. In nitrogen compounds:

• In NO₂⁺, the linear shape results from sp hybridization, with electrons spread 180 degrees apart.
• The trigonal planar shape of NO₃^- comes from sp² hybridization, with electrons at 120-degree angles spaced evenly.
• NH₄⁺ forms a tetrahedral shape due to sp³ hybridization, which positions electrons 109.5 degrees apart.

Knowing the molecular geometry aids in predicting the behavior of molecules during chemical reactions. It also impacts properties like polarity and intermolecular forces.

Steric Number

The steric number is an essential index for understanding hybridization and molecular geometry. It represents the total number of regions of electron density (bonds and lone pairs) surrounding a central atom. The steric number allows chemists to predict how atoms will hybridize. Here's how it works in context:

• A steric number of 2 correlates with sp hybridization. This is seen in NO₂⁺.
• A steric number of 3 corresponds to sp² hybridization and applies to NO₃^-.
• For NH₄⁺, with a steric number of 4, the hybridization is sp³.

Understanding the steric number helps determine not just the hybridization but also the 3D structural features of the compound. This makes it a fundamental concept in chemistry, critical for predicting and explaining molecular shapes and behaviors.