Question

Decide which bond in each pair is polar and explain your reasoning. Place \(\delta+\) and \(\delta\) - superscripts on the element symbols for each polar bond to indicate the direction of the polarity. (a) \(\mathrm{F}-\mathrm{F}\) and \(\mathrm{C}-\mathrm{F}\) (c) \(\mathrm{O}-\mathrm{O}\) and \(\mathrm{N}-\mathrm{O}\) (b) \(\mathrm{O}-\mathrm{H}\) and \(\mathrm{H}-\mathrm{H}\)

Short answer

Polar bonds occur in C-F, N-O, and O-H, with polarity directions as C(\(\delta^+\))-F(\(\delta^-\)), N(\(\delta^+\))-O(\(\delta^-\)), and H(\(\delta^+\))-O(\(\delta^-\)). The bonds in F-F, O-O, and H-H are nonpolar as they consist of identical atoms with equal electronegativity.

Step-by-step solution

Identifying Polar and Nonpolar Bonds

Compare the electronegativity of atoms for each given pair.

F-F and C-F

The bond between two atoms of the same element, such as F-F, is nonpolar because the electrons are equally distributed between both atoms. The bond between C and F is polar because F is more electronegative than C. Thus, F carries the partial negative charge (\(\delta^-\)) and C carries the partial positive charge (\(\delta^+\)).

O-O and N-O

The bond in O-O is nonpolar because both atoms are identical. Between N and O, O is more electronegative hence it carries a partial negative charge (\(\delta^-\)) and N carries the partial positive charge (\(\delta^+\)).

O-H and H-H

The bond in H-H is nonpolar as both the atoms are identical. The bond between O and H is polar, because O is more electronegative. Therefore, O acquires a partial negative charge (\(\delta^-\)) and H acquires the partial positive charge (\(\delta^+\)).

Key concepts

Understanding Electronegativity

Electronegativity is a fundamental concept in chemistry that describes an atom's ability to attract and hold onto electrons in a chemical bond. This property varies across the periodic table, generally increasing as you move from left to right across a period and decreasing as you move down a group.

When two atoms form a bond, their relative electronegativities determine whether the bond will be polar or nonpolar:

• In a nonpolar bond, such as \(\mathrm{F}-\mathrm{F}\) or \(\mathrm{O}-\mathrm{O}\), both atoms have equal electronegativity, leading to an equal sharing of electrons.
• In a polar bond, like \(\mathrm{C}-\mathrm{F}\) or \(\mathrm{N}-\mathrm{O}\), one atom is more electronegative and attracts shared electrons more strongly, creating partial positive and negative charges (\(\delta^+\) and \(\delta^-\)) on the atoms involved.

Understanding electronegativity helps predict the behavior and properties of molecules in chemical reactions and interactions.

Exploring Molecular Polarity

Molecular polarity arises from the presence of polar bonds and the geometric arrangement of these bonds within a molecule. It's essential in determining the physical and chemical properties of substances, such as solubility and boiling point.

If a molecule contains polar bonds arranged asymmetrically, the molecule itself becomes polar, meaning it has a net dipole moment:

• Molecules like \(\mathrm{H}-\mathrm{H}\) and \(\mathrm{O}-\mathrm{O}\) are nonpolar because they consist of identical atoms with no difference in electronegativity and therefore no net dipole moment.
• Molecules like \(\mathrm{O}-\mathrm{H}\) have polar bonds, and their structure typically leads to a polar molecule overall, impacting how they interact with other molecules.

Molecular polarity is crucial in fields ranging from biochemistry to material science, influencing how molecules behave and interact on a microscopic level.

Insights into Chemical Bonding

Chemical bonding is the force that holds atoms together in compounds. It results from the sharing or transferring of electrons between atoms, leading to the formation of stable molecules.

There are different types of chemical bonds, each with distinct characteristics:

• **Covalent Bonds** - These involve the sharing of electron pairs between atoms. They can be nonpolar, as seen in \(\mathrm{H}-\mathrm{H}\) and \(\mathrm{O}-\mathrm{O}\), or polar, like \(\mathrm{O}-\mathrm{H}\) or \(\mathrm{C}-\mathrm{F}\), depending on the electronegativity difference.
• **Ionic Bonds** - Here, electrons are transferred from one atom to another, typically between metals and non-metals, resulting in oppositely charged ions that attract each other.

Understanding chemical bonding is foundational for predicting the structure, properties, and reactions of molecules, which is essential for advances in chemistry and related sciences.