Question

In 1999, an unusual cation containing only nitrogen \(\left(\mathrm{N}_{5}^{+}\right)\) was prepared. Draw three resonance structures of the ion, showing formal charges.

Short answer

Three resonance structures distributed positive charge by altering double bond positions between nitrogen atoms.

Step-by-step solution

Understand the Structure

The cation consists of five nitrogen atoms, and the objective is to draw resonance structures displaying various distributions of electrons that still respect the overall positive charge.

Determine Formal Charges

Each nitrogen atom can form three bonds and carry one lone pair in the neutral state. In a resonance structure, adjust the bonds and lone pairs among the five nitrogen atoms to ensure that the formal charges add up to +1, the charge of the ion.

Draw the Initial Structure

Start with a linear chain of five nitrogen atoms bonded together. Assign double bonds between some adjacent nitrogen atoms so that the octet rule is satisfied for each, and calculate the formal charges to ensure the sum of all charges is +1.

Create First Resonance Structure

Place a double bond between N1 (the first nitrogen) and N2, another between N3 and N4, and allow for single bonds elsewhere. Assign formal charges making sure the middle nitrogen (N3) carries a '+1' charge and the others have formal charges that balance to zero as much as possible.

Generate Second Resonance Structure

Shift the position of the double bonds to create an alternate contributing structure where N2 and N3 have a double bond, as well as N4 and N5. Reallocate electrons (lone pairs) to ensure formal charges are distributed with one nitrogen atom carrying the positive charge.

Develop Third Resonance Structure

Make further adjustments by placing double bonds between N1 and N2, and N4 and N5. Recalculate the formal charges so N5 carries the positive charge, ensuring the total charge remains +1.

Key concepts

Understanding Cation Chemistry

Cation chemistry is an essential area in the field of chemistry where the focus is on ions carrying a positive charge. These are called cations, which occur when an atom, or a group of atoms, lose one or more electrons resulting in a net positive charge. Understanding cation chemistry involves exploring how these cations form, interact, and stabilize.

In the case of nitrogen, which usually forms covalent bonds by sharing electrons to fulfill the octet rule, forming a cation can be quite unique. When nitrogen forms a cation such as \(_5^+\), it loses an electron, leading to a positive charge. Cations like \(_5^+\) can form interesting structures called resonance structures. These structures are ways of depicting the same molecule by showing different electron arrangements to reflect the distribution of the positive charge in various ways.

In essence, the chemistry of cations is critical for understanding not only simple ions but also complex molecular ions. This understanding aids in predicting reactions, stability, and the magnetic properties of molecules.

Exploration of Formal Charge Calculation

Determining the formal charge, especially in structures like cations and resonance structures, is crucial for predicting the distribution of the electron clouds in a given molecule. The formal charge allows us to assess which atoms carry a positive, negative, or neutral charge, and ensures that the structure we depict is consistent with the known electronic properties of the atoms involved.

The formula for calculating the formal charge is quite simple:

• Formal Charge = (Valence electrons of atom) - (Non-bonding electrons + 1/2 Bonding electrons)

Using this, we can determine how electrons are distributed in molecular structures and ensure they obey the laws of chemistry, such as ensuring the sum of the formal charges in a molecule equals its total charge.

For example, in \(_5^+\), adjustments in electron distribution around nitrogen atoms affect their formal charges. By varying which atoms possess double or single bonds, and by shifting lone pairs, we can generate different resonance structures each with unique but valid formal charge distributions that add up to the overall charge of +1.

Insight into Nitrogen Compounds

Nitrogen compounds play a vital role in chemistry due to nitrogen’s ability to form a wide variety of bonds. Nitrogen, with its five valence electrons, can form up to three covalent bonds, making it versatile in building complex structures.

In nitrogen cations like \(_5^+\), where nitrogen atoms form a chain, each nitrogen typically participates in both single and double covalent bonds, leading to unique structures. These structures must satisfy the octet rule, either strictly or through resonance which shares electron density across the molecule. This behavior is key to nitrogen's identity, impacting how nitrogen compounds react and stabilize.

Resonance structures of nitrogen compounds highlight this ability as they illustrate different electron configurations that are possible due to nitrogen's variable bonding capacity. This flexibility of forming different compounds makes nitrogen indispensable in both organic and inorganic chemistry, impacting fields ranging from pharmaceuticals to fertilizers.