Question

Write the Lewis structure for nitrosyl fluoride, FNO. Using only a periodic table, identify (a) which is the longer bond. (b) which is the stronger bond. (c) which is the more polar bond.

Short answer

(a) N-F is longer; (b) N-O is stronger; (c) N-F is more polar.

Step-by-step solution

Count Valence Electrons

We first count the total number of valence electrons available: - Fluorine (F) has 7 valence electrons. - Nitrogen (N) has 5 valence electrons. - Oxygen (O) has 6 valence electrons. Thus, the total number of valence electrons is 7 + 5 + 6 = 18 electrons.

Determine Electron Pairing

Arrange the atoms in order: F-N-O. Assign unshared pairs and bond pairs to account for the 18 valence electrons: - Create a single bond between N-F and a double bond between N-O. - Allocate the remaining electrons as lone pairs to complete the octet of each atom. - Lewis structure: - F with 3 lone pairs. - N forms a single bond with F and a double bond with O. - O with 2 lone pairs.

Compare Bond Lengths

In general, bond length is inversely related to bond order. - The bond between N and O is a double bond, which is shorter than a single bond. - The bond between N and F is a single bond. Therefore, the N-F bond is longer than the N-O bond.

Assess Bond Strength

Stronger bonds usually have higher bond orders. - The N-O bond is a double bond, which is generally stronger than the N-F single bond. Thus, the N-O bond is stronger than the N-F bond.

Evaluate Bond Polarity

Polarity is influenced by the difference in electronegativity between two atoms: - The electronegativity of F is 3.98, N is 3.04, and O is 3.44 according to the Pauling scale. - The difference between N and F is 3.04 - 3.98 = -0.94. - The difference between N and O is 3.04 - 3.44 = -0.40. Thus, the N-F bond is more polar than the N-O bond, since it has a larger difference in electronegativity.

Key concepts

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a crucial role in chemical bonding. For molecules like nitrosyl fluoride (FNO), calculating valence electrons is a key step in determining the Lewis structure. Each element contributes a specific number of valence electrons based on its position in the periodic table.

For example:

• Fluorine (F) is in Group 17 and has 7 valence electrons.
• Nitrogen (N) is in Group 15 and has 5 valence electrons.
• Oxygen (O) is in Group 16 and has 6 valence electrons.

Totaling up these valence electrons (7 from F, 5 from N, and 6 from O) gives us 18 electrons. These electrons are then used to form bonds and complete the octets in each atom, ensuring that every atom achieves a stable electron configuration.

Understanding how to calculate and use valence electrons helps in predicting molecule shapes, bond types, and overall reactivity.

Bond Length

Bond length is the distance between the nuclei of two bonded atoms. It is affected by the bond order, which is the number of shared electron pairs between atoms. Generally, the higher the bond order, the shorter the bond length. For example, triple bonds are shorter than double bonds, which in turn are shorter than single bonds.

In nitrosyl fluoride, FNO:

• The N-F bond is a single bond.
• The N-O bond is a double bond.

The N-O double bond is shorter than the N-F single bond because double bonds share more electrons, pulling the atoms closer together. Recognizing bond lengths helps in understanding the physical and chemical properties of a molecule, such as reactivity and interaction with other molecules.

Bond Strength

Bond strength refers to the energy required to break a bond between two atoms. Stronger bonds have higher bond energies and are thus harder to break. Typically, bond strength is directly proportional to bond order; higher bond orders mean stronger bonds.

In nitrosyl fluoride:

• The N-O double bond is stronger than the N-F single bond.

This strength arises because each atom in a double bond shares more electrons, providing a greater "holding power" between the atoms. Hence, molecules with higher bond strengths tend to be more chemically stable.

Understanding bond strength is important in determining reaction pathways and stability of compounds.

Bond Polarity

Bond polarity arises from differences in electronegativity between bonded atoms. Electronegativity is a measure of an atom's ability to attract shared electrons. When two atoms bonded together have different electronegativities, the electrons are more attracted to one atom, creating a dipole moment.

In nitrosyl fluoride, we see this concept in action:

• Fluorine (F) is highly electronegative with a value of 3.98.
• Nitrogen (N) has an electronegativity value of 3.04.
• Oxygen (O) comes in between at 3.44.

The N-F bond, with an electronegativity difference of 0.94, is more polar compared to the N-O bond, which has a difference of 0.40. This larger electronegativity difference in the N-F bond causes greater polarity, where electrons are pulled more toward the highly electronegative fluorine atom. Understanding bond polarity is essential in predicting molecule interactions, solubilities, and reaction mechanisms.