Recall What are the requirements for molecules to form hydrogen bonds? (What atoms must be present and involved in such bonds?)

Electronegativity is a measure of how strongly an atom can attract and hold onto electrons.
This is an important concept in chemistry, as it helps determine how atoms will interact with each other in a molecule.
In the context of hydrogen bonds, electronegativity plays a key role.

Certain elements like nitrogen (N), oxygen (O), and fluorine (F) have high electronegativity.
When hydrogen is covalently bonded to any of these elements, it results in an unequal sharing of electrons.
The highly electronegative atom will attract the shared electrons more towards itself, leaving the hydrogen atom with a partial positive charge.
This capability to create such partial charges is essential for forming hydrogen bonds.

A partial charge arises when there is an unequal sharing of electrons in a covalent bond.
This is often due to the difference in electronegativity between the bonding atoms.
In a water molecule, for example, oxygen is more electronegative than hydrogen.
As a result, the shared electrons are pulled closer to the oxygen, creating a partial negative charge (δ−) on the oxygen and a partial positive charge (δ+) on the hydrogen.

These partial charges are crucial for hydrogen bonding.
The partially positive hydrogen atom will be attracted to the partially negative atom (like nitrogen, oxygen, or fluorine) in a nearby molecule.
This attraction is what we call a hydrogen bond.
Though weaker than covalent bonds, hydrogen bonds are significant in maintaining the structure and properties of molecules like water and nucleic acids.

Covalent bonding is a type of chemical bond where two atoms share a pair of electrons.
Unlike ionic bonding, where electrons are transferred from one atom to another, covalent bonds involve the sharing of electron pairs between atoms.
This electron sharing usually occurs between non-metal atoms.

In hydrogen bonds, the hydrogen atom must first form a covalent bond with a highly electronegative atom (N, O, or F).
This covalent bond is the foundation for creating the partial positive charge on the hydrogen atom.
The higher electronegativity of N, O, or F pulls the bonding electrons closer to it, thereby partially stripping electrons from hydrogen.
This arrangement is what makes the hydrogen atom slightly positive and capable of forming a hydrogen bond with another electronegative atom nearby.

Remember, the initial covalent bond is essential because it creates the necessary conditions—partial charges—that facilitate hydrogen bonding.