Video: Identifying the Type of Bond between Water Molecules in a Set of Bond Types

Which of the following is the type of bond between two water molecules? [A] Hydrogen bond [B] Ionic bond [C] Polar covalent bond [D] Nonpolar covalent bond [E] Metallic bond

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Video Transcript

Which of the following is the type of bond between two water molecules? (A) Hydrogen bond, (B) ionic bond, (C) polar covalent bond, (D) nonpolar covalent bond, or (E) metallic bond.

A bond, or chemical bond, is a strong force of attraction holding atoms or ions together. A hydrogen bond is an example of an intermolecular bond. And ionic, polar covalent, nonpolar covalent, and metallic bonds are examples of intramolecular bonds.

Inter- in intermolecular bond means between. So, an intermolecular bond, such as a hydrogen bond, is the bond or force of attraction between two separate molecules. Intra- in the term intramolecular bonds means within. So, an intramolecular bond is a bond or force of attraction within an individual unit of a compound, such as a molecule or a formula unit.

The question asks for the type of bond between two water molecules, in other words, an intermolecular bond. Of the possible answers, only (A), hydrogen bond, is an example of an intermolecular bond. Let’s confirm this by discussing what a hydrogen bond is. Water, or H2O, is a bent molecule. The electronegativity value of oxygen is much higher than that of hydrogen. Oxygen has a value of 3.4 and hydrogen a value of 2.2.

Electronegativity is the tendency of an atom to attract a bonding pair of electrons towards itself. Because oxygen has a higher electronegativity value, this means that oxygen pulls the bonding pair of electrons more strongly towards itself than does hydrogen. This pull on the bonding electrons results in the electrons spending more time in the vicinity of the oxygen atom. And the oxygen atom becomes Δ negative or slightly negatively charged and the hydrogen atom Δ positive or slightly positively charged. This slight charge distribution will happen for every bond in the water molecules of a sample.

The slightly positively charged hydrogen atom on one water molecule becomes electrostatically attracted to the slightly negatively charged oxygen atom on an adjacent water molecule. This electrostatic attraction between separate molecules as a result of the Δ positive and Δ negative charges is called a hydrogen bond. So, the type of bond between two water molecules is option (A), hydrogen bond. Let’s very briefly remind ourselves of ionic, polar covalent, nonpolar covalent, and metallic bonds.

An ionic bond occurs when a metal cation and a nonmetal anion electrostatically attract each other, for example, in sodium chloride, Na+ and Cl−. A polar covalent bond exists between two nonmetals when the electronegativity difference is between 0.4 and 1.8. An example is the bond within a water molecule. A nonpolar covalent bond exists between two nonmetals when the electronegativity difference is less than 0.4 and the pull on the bonding electrons is equal or almost equal, for example, in Cl2 or chlorine gas. Finally, a metallic bond exists in metals, for example, iron, where a sea of electrons holds the positively charged nuclei of the atoms together.

And the final answer is (A), hydrogen bond.

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