Question

Determine whether each of the following bonds would be polar or nonpolar: a. \(\mathrm{H}-\mathrm{H}\) b. \(\mathrm{H}-\mathrm{O}\) c. \(\mathrm{H}-\mathrm{F}\) d. \(\mathrm{Br}-\mathrm{Br}\) e. \(\mathrm{H}-\mathrm{Cl}\) f. \(\mathrm{H}-\mathrm{N}\)

Short answer

a. Nonpolar, b. Polar, c. Polar, d. Nonpolar, e. Polar, f. Polar

Step-by-step solution

Definition of Polar and Nonpolar Bonds

Polar bonds occur when there is a significant difference in electronegativity between two atoms, causing a dipole moment. Nonpolar bonds occur when the two atoms have similar or identical electronegativity, resulting in an equal sharing of electrons.

Checking \(\mathrm{H}-\mathrm{H}\) Bond

The bond between two hydrogen atoms \(\mathrm{H}-\mathrm{H}\) has identical electronegativity values. Therefore, the electrons are shared equally, making this bond nonpolar.

Checking \(\mathrm{H}-\mathrm{O}\) Bond

Oxygen is more electronegative than hydrogen. The difference in electronegativity causes an unequal sharing of electrons, making the \(\mathrm{H}-\mathrm{O}\) bond polar.

Checking \(\mathrm{H}-\mathrm{F}\) Bond

Fluorine is significantly more electronegative than hydrogen. The large difference results in a highly polar bond \(\mathrm{H}-\mathrm{F}\).

Checking \(\mathrm{Br}-\mathrm{Br}\) Bond

The bond between two bromine atoms \(\mathrm{Br}-\mathrm{Br}\) has identical electronegativity values. Thus, it is a nonpolar bond.

Checking \(\mathrm{H}-\mathrm{Cl}\) Bond

Chlorine is more electronegative than hydrogen, creating a difference in electronegativity. This makes the \(\mathrm{H}-\mathrm{Cl}\) bond polar.

Checking \(\mathrm{H}-\mathrm{N}\) Bond

Nitrogen is more electronegative than hydrogen, resulting in a polar \(\mathrm{H}-\mathrm{N}\) bond due to the unequal sharing of electrons.

Key concepts

Electronegativity

Electronegativity is the ability of an atom to attract electrons towards itself in a chemical bond. It is a key concept in understanding polar and nonpolar bonds.

Different elements have different electronegativity values. For example:

• Fluorine has the highest electronegativity.
• Oxygen also has a high electronegativity.
• Hydrogen and bromine have lower electronegativities.

When two atoms with different electronegativity form a bond, the more electronegative atom attracts the shared electrons more strongly.
This causes a partial negative charge at the more electronegative atom and a partial positive charge at the other atom.
This creates a polar bond.

In contrast, if the two atoms have similar or identical electronegativities, they share electrons equally, leading to a nonpolar bond.

Dipole Moment

A dipole moment is a measure of the separation of positive and negative charges in a molecule. It indicates how polar the bond or molecule is.

For example, in the \(\text{H-O}\) bond, oxygen has a higher electronegativity than hydrogen.
This causes the electrons to be drawn more towards oxygen, creating a dipole moment. The molecule exhibits a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atom.

The larger the difference in electronegativity between the bonded atoms, the larger the dipole moment.
Strong dipole moments lead to high polarity.

Nonpolar molecules or bonds have no dipole moment because the electron distribution is symmetrical. For example, in the \(Br-Br\) bond, both bromine atoms have identical electronegativities. This results in no difference in electron distribution, giving no dipole moment, hence a nonpolar bond.

Covalent Bonds

Covalent bonds are formed when two atoms share electrons to achieve a stable electron configuration. There are two main types of covalent bonds: polar and nonpolar.

- **Nonpolar Covalent Bonds:** These occur when two atoms share electrons equally. This happens when the atoms involved have similar or identical electronegativities. For instance, in the \(H-H\) and \(Br-Br\) bonds, the atoms involved share electrons equally, resulting in nonpolar covalent bonds.

- **Polar Covalent Bonds:** These occur when there is an unequal sharing of electrons between two atoms due to a difference in their electronegativities. This results in a partial negative charge on the more electronegative atom and a partial positive charge on the other atom. Examples of polar covalent bonds include \(H-O\), \(H-F\), \(H-Cl\), and \(H-N\).

Understanding covalent bonds is essential for studying molecule structures and their properties.