Question

The maximum possible number of hydrogen bonds a water molecule can form is (1) 1 (2) 2 (3) 3 (4) 4

Short answer

4

Step-by-step solution

Understanding Hydrogen Bonds in Water

A hydrogen bond is a type of weak attraction between a slightly positive hydrogen atom and a slightly negative atom, such as oxygen. Water (H2O) molecules form hydrogen bonds due to the polarity of the molecules.

Structure of a Water Molecule

Each water molecule consists of one oxygen atom and two hydrogen atoms. The oxygen atom is more electronegative than the hydrogen atoms, leading to a partial negative charge on the oxygen and partial positive charges on the hydrogens.

Hydrogen Bond Formation

A water molecule can potentially form hydrogen bonds with four other water molecules. The oxygen atom can form hydrogen bonds with two hydrogen atoms from two different water molecules, and each hydrogen atom can form a hydrogen bond with the oxygen atoms from two other water molecules.

Count the Bonds

Summarizing the above, each water molecule can form a total of four hydrogen bonds: two from the hydrogen atoms and two from the oxygen atom providing hydrogen bonds to other hydrogen atoms from other water molecules.

Key concepts

Water Molecule Structure

Water, known chemically as H₂O, consists of one oxygen atom and two hydrogen atoms. These atoms are bonded together through covalent bonds, where the atoms share electrons. However, the atoms do not share these electrons equally. Because oxygen is more electronegative, it pulls the shared electrons closer to itself, resulting in an uneven distribution of charge within the molecule. As a result, the oxygen end of the molecule has a slight negative charge, and the hydrogen ends have a slight positive charge.

Polarity of Molecules

Polarity refers to the distribution of electrical charges within a molecule. When a molecule has regions with distinct positive and negative charges, it is considered polar. Water is a classic example of a polar molecule because of its V-shaped structure and uneven charge distribution. The oxygen atom, being more electronegative, pulls the electrons closer, creating a partial negative charge. The hydrogen atoms, on the other hand, are left with partial positive charges. This polarity allows water molecules to interact with each other through hydrogen bonds, where the positive end of one molecule is attracted to the negative end of another.

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold on to electrons. In water, the oxygen atom has a higher electronegativity compared to the hydrogen atoms. This means oxygen has a stronger pull on the shared electrons in the covalent bonds. Due to this difference in electronegativity, the oxygen atom develops a slight negative charge, while the hydrogen atoms develop slight positive charges. This difference is crucial for the formation of hydrogen bonds in water, as these partial charges attract the opposite charges in other water molecules, leading to the characteristic hydrogen bonding. Each water molecule can form four hydrogen bonds because of these shared electronegative properties.