Question

The deadly poison hydrogen cyanide has the chemical formula \(\mathrm{H}-\mathrm{C} \equiv \mathrm{N}\). Describe the bonds between carbon and hydrogen and between carbon and nitrogen in terms of the number of electrons involved.

Short answer

There is a single bond between Carbon and Hydrogen that contains 2 electrons (1 from each atom) and a triple bond between Carbon and Nitrogen which contains 6 electrons (3 from each atom).

Step-by-step solution

Understanding the Lewis Dot Structure

Lewis Structures are diagrams that depict the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule. A single line indicates a single bond, while a triple line indicates a triple bond. The chemical formula for Hydrogen Cyanide (HCN) will help in drawing the Lewis structure. Hydrogen (H) has one electron, Carbon (C) has six electrons, and Nitrogen (N) has five electrons.

Creating the Lewis Structure

First, arrange the atoms to show specific connections. Hydrogen always goes on the outside, so Hydrogen (H) is bonded to Carbon (C), and Carbon (C) is then bonded to Nitrogen (N). The structure should look like H-C≡N. Next, determine how many electrons should be represented in the structure. Add up the valance electrons from each atom. Hydrogen has 1, Carbon has 4 and Nitrogen has 5, for a total of 10 electrons that should be represented. Now, arrange the electrons in pairs around each atom so that the inner atom's shells are filled. Hydrogen needs only 2 electrons to fill its shell (it contributes 1 and gets 1 from Carbon), Carbon gets 4 from the triple bond with Nitrogenand contributes 1 for the Hydrogen and Nitrogen and Nitrogen brings 5 to have a full octet.

Identifying the Type of Bonds

From the Lewis structure H-C≡N, there is a single bond between Hydrogen (H) and Carbon (C), so there are 2 electrons involved in this bond (1 from Hydrogen and 1 from Carbon). There is a triple bond between Carbon (C) and Nitrogen (N), so there are 6 electrons involved in this bond (3 pairs: 3 from Carbon and 3 from Nitrogen).

Key concepts

Chemical Bonding

Chemical bonding is a fascinating process that involves the interaction of atoms to form molecules. It mainly includes covalent, ionic, and metallic bonds. This exercise focuses on covalent bonds, where atoms share electrons to achieve stability. In hydrogen cyanide (HCN), both single and triple covalent bonds are present, illustrating the diversity within molecular structures.

When hydrogen and carbon form a single bond, they share one pair of electrons, drawing them together. This kind of bond is quite straightforward, involving two electrons in total—one from each atom. It offers a stable connection while allowing the unique properties of hydrogen to complement carbon.

Contrastively, the triple bond between carbon and nitrogen involves sharing three pairs of electrons. Such a bond is much stronger and brings the atoms very close. As each atom shares three electrons, it satisfies the octet rule for stability. This bond greatly affects the characteristics of the molecule, influencing its strength and reactivity.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial for bonding. They determine how atoms will bond and interact with each other, as they are the electrons involved in forming chemical bonds.

In hydrogen cyanide, calculating the number of valence electrons tells us how these atoms achieve stable electron configurations. Hydrogen has 1 valence electron, carbon has 4, and nitrogen has 5. Adding them gives us a total of 10 valence electrons, which need to be arranged to optimize stability under the octet rule.

• Hydrogen: Needs 2 electrons, achieves this with a single bond to carbon.
• Carbon: Requires 8 electrons, gains these through 1 bond with hydrogen and 3 bonds with nitrogen.
• Nitrogen: Also aims for 8 electrons, completes this with the triple bond to carbon.

Understanding valence electrons allows us to draw accurate conclusions on how these bonds are likely to form and what shape the molecules will take.

Molecular Structure

Molecular structure refers to the arrangement of atoms within a molecule, dictating the molecule's shape, angle, and properties. For HCN, we can visualize it as a linear structure due to the mathematics and geometry of its bond angles.

A linear structure emerges when there is a straight line across the atoms, which in the case of HCN is facilitated by the strong triple bond between carbon and nitrogen. This configuration imparts certain chemical properties, including effectiveness in delocalizing charge and stability, contributing to the molecule's overall behavior and characteristics.

The Lewis structure provides a visual guide to understanding this arrangement, displaying bonds and electron pairs clearly. By organizing these electrons properly, we predict molecular reactivity and stability.