Question

A few years ago the synthesis of a salt containing the \(\mathrm{N}_{5}^{+}\) ion was reported. What is the likely shape of this ion-linear, bent, zigzag, tetrahedral, seesaw, or square-planar? Explain your choice.

Short answer

The likely shape of the \(\mathrm{N}_{5}^{+}\) ion is tetrahedral.

Step-by-step solution

Determine the Lewis Structure

We first determine the Lewis structure of the \(\mathrm{N}_{5}^{+}\) ion. The Lewis structure is a simple depiction of covalent bonds and valence electrons in a molecule. With the N5+ ion, nitrogen has 5 valence electrons and it forms bonds with other 4 nitrogen atoms. This leaves it with a positive charge due to loss of an electron during bond formation.

Identify the central atom

From the Lewis structure, identify the central atom. Here, the central atom is Nitrogen.

Count valence electron pairs

Count the atoms attached to the central atom and lone pairs. The central Nitrogen is surrounded by four other Nitrogens and has no lone pairs.

Applying VSEPR theory

Use the VSEPR theory concept which states that electron pairs around an atom arrange themselves in such a way to minimize repulsion. Here, With 4 bonding pairs of electrons around the central nitrogen, it leads to a tetrahedral arrangement to minimize the repulsion between these electron pairs.

Predict the shape

Based on the VSEPR theory, the predicted shape of this molecule is tetrahedral as it minimizes the repulsion between the bonding pairs of electrons.

Key concepts

Lewis structure

The Lewis structure is a foundational tool in chemistry that represents the distribution of electrons in molecules. It visually depicts the bonds between atoms and the lone pairs of electrons in a molecule. By sketching a Lewis structure, one can identify how atoms are bonded in a molecule and predict the locations of lone pairs of electrons.

In the case of the \(_5^+\) ion, its Lewis structure involves a central nitrogen atom bonding covalently with four other nitrogen atoms. This configuration is necessary to visualize how \(_5^+\) attains stability despite having a net positive charge. The surplus positive charge occurs because the central nitrogen atom loses an electron during bond formation.

valence electrons

Valence electrons are the outermost electrons of an atom. They are crucial in determining an atom's bonding behavior, particularly in covalent connections. In the periodic table, group 5 elements like nitrogen possess five valence electrons.

For the \(_5^+\) ion, the nitrogen at the center uses its 5 valence electrons to form bonds with the surrounding nitrogen atoms. Normally, nitrogen has 5 valence electrons, but in the \(_5^+\) structure, one is lost, contributing to its positive charge. Understanding this electron loss helps in analyzing how the ion is formed and its overall structure remains stable.

molecular geometry

Molecular geometry describes the three-dimensional arrangement of atoms in a molecule. It is primarily determined by the number of bonded atoms and lone electron pairs around a central atom.

The VSEPR (Valence Shell Electron Pair Repulsion) theory suggests that electron pairs, both lone pairs and bonding pairs, will position themselves to minimize repulsion. In the \(_5^+\) ion, the central nitrogen is surrounded by four other nitrogen atoms with no lone pairs. This leads to a tetrahedral geometry, where each bond angle is approximately 109.5 degrees. This arrangement minimizes electron pair repulsion, optimizing the stability of the ion's structure.

electron pairs

Electron pairs in molecules can be bonding or non-bonding (lone pairs). They play a key role in determining molecular shape and stability. Bonding pairs are involved in the actual connections between atoms, while lone pairs affect molecular geometry by repelling other electrons.

• In the \(_5^+\) ion, all electron pairs around the central nitrogen atom are bonding pairs.
• There are no lone pairs, which simplifies predicting its molecular shape.

The presence of four bonding electron pairs around a central atom leads to a well-defined shape such as tetrahedral, allowing for minimal repulsion and maximum stability of the ion.