Question

In addition to water and ammonia, what small diatomic molecule forms strong hydrogen bonds?

Short answer

Hydrogen fluoride (HF) forms strong hydrogen bonds.

Step-by-step solution

Understand Hydrogen Bonding

Hydrogen bonding occurs when a hydrogen atom is covalently bonded to a highly electronegative atom, such as nitrogen, oxygen, or fluorine. This leads to a partial positive charge on the hydrogen, allowing it to interact with lone pairs on electronegative atoms in other molecules, forming a hydrogen bond.

Identify Candidates

Common diatomic molecules include oxygen (O2), nitrogen (N2), fluorine (F2), chlorine (Cl2), and hydrogen (H2). Among these, we need to find one that can form strong hydrogen bonds.

Evaluate Diatomic Molecules

Out of the diatomic molecules, we identify hydrogen fluoride (HF), as it contains hydrogen and the highly electronegative fluorine atom (F), which is capable of forming strong hydrogen bonds due to its high electronegativity.

Key concepts

Electronegativity

Electronegativity is a fundamental chemical property that tells us how strongly an atom can attract electrons in a chemical bond. Atoms with high electronegativity values tend to pull shared electrons in a covalent bond closer to themselves.
This results in a partial negative charge on the more electronegative atom, while the other atom receives a partial positive charge. In the periodic table, electronegativity tends to increase from left to right across a period and decrease down a group. Fluorine is the most electronegative element, followed by oxygen and nitrogen. These elements play a significant role in forming hydrogen bonds. To sum up, electronegativity is a key concept for understanding many chemical interactions, including the formation of hydrogen bonds.

Diatomic Molecules

Diatomic molecules consist of two atoms bonded together. These can be either homonuclear, with two atoms of the same element, like oxygen ( O_2 ), or heteronuclear, with two different elements, such as hydrogen chloride (HCl). Diatomic molecules can be found in all states of matter, but several common ones, like nitrogen ( N_2 ) and oxygen ( O_2 ), exist as gases at room temperature. A few simple characteristics of diatomic molecules include:

• They can be elements like hydrogen ( H_2 ) that naturally occur as diatomic molecules.
• They often exhibit unique physical properties, such as low boiling points.
• They play essential roles in atmospheric chemistry and are crucial to life on earth.

Overall, diatomic molecules are some of the simplest but most important building blocks of chemistry.

Hydrogen Bonding in HF

Hydrogen bonding is a unique type of interaction that can heavily influence the properties of a compound. One of the prime examples is hydrogen fluoride (HF), which exhibits strong hydrogen bonds due to fluorine's high electronegativity.

How Hydrogen Bonding Works in HF

In HF, the hydrogen atom is covalently bonded to a fluorine atom. This bond results in a highly polarized molecule, with a partial positive charge on hydrogen and a partial negative charge on fluorine.
This polarization allows the hydrogen atom to interact with lone pairs of electrons on fluorine atoms in nearby molecules, forming hydrogen bonds.

Impact on Physical Properties

The strong hydrogen bonding in HF gives it some unusual physical properties compared to other diatomic molecules. For instance, HF has a much higher boiling point than expected for such a small molecule. This is because a significant amount of energy is required to break the hydrogen bonds during vaporization. In summary, the strong hydrogen bonding present in HF is a direct result of the high electronegativity of fluorine, which creates a robust interaction that heavily influences HF's properties.