Problem 47 - Chemistry The Central Science In Si Units

Question

For each statement, indicate whether it is true or false. (a) The greater the orbital overlap in a bond, the weaker the bond. (b) The greater the orbital overlap in a bond, the shorter the bond. \((\mathbf{c})\) To create a hybrid orbital, you could use the \(s\) orbital on one atom with a \(p\) orbital on another atom. (d) Nonbonding electron pairs cannot occupy a hybrid orbital.

Step-by-Step Solution

Answer

(a) False, (b) True, (c) False, (d) False.

Step 1: Understanding Orbital Overlap

Orbital overlap refers to the extent to which orbitals on bonded atoms occupy the same region of space, allowing electron sharing between atoms. This overlap can affect the strength and length of the bond.

Step 2: Evaluating Statement (a)

Statement (a) claims that the greater the orbital overlap, the weaker the bond. This is false. Greater orbital overlap generally results in a stronger bond because more electron density is shared between the atoms.

Step 3: Evaluating Statement (b)

Statement (b) claims that the greater the orbital overlap, the shorter the bond. This is true. Greater overlap typically indicates a stronger attraction between atoms, pulling them closer together and resulting in a shorter bond.

Step 4: Evaluating Statement (c)

Statement (c) suggests creating a hybrid orbital by combining an s orbital from one atom with a p orbital from another atom. This is false. Hybrid orbitals are formed from combining orbitals on the same atom, not between different atoms.

Step 5: Evaluating Statement (d)

Statement (d) claims nonbonding electron pairs cannot occupy a hybrid orbital. This is false. Nonbonding electron pairs can occupy hybrid orbitals, as they often do in molecules like ammonia (NH₃), where lone pairs occupy hybrid orbitals.

Key Concepts

Bond Strength

Bond strength is a measure of how strongly atoms are bonded together. It is determined by the energy required to break the bond between two atoms. The greater the overlap between the orbitals of the bonded atoms, the stronger the bond. This is because more electron density is shared between them, increasing the electrostatic attraction. When atoms share a large overlap of orbitals, it indicates a high electron sharing and a robust bond formation.

• Increased orbital overlap means increased bond strength.
• Stronger bonds require more energy to break.
• Strong bonds are often found in stable molecules.

Understanding bond strength can help predict the stability and reactivity of molecules.

Bond Length

Bond length is the distance between the nuclei of two bonded atoms. The bond length is influenced by the amount of orbital overlap. Greater orbital overlap results in a shorter bond length because the strong attraction pulls the atoms closer together. This is due to the increased electron density between the atoms, which shortens the distance between the nuclei.

• Greater overlap results in shorter bond lengths.
• Short bond lengths are often associated with strong bonds.
• Shorter bonds generally indicate greater force holding the atoms together.

When comparing similar types of bonds, those with shorter bond lengths are typically stronger and more stable.

Hybrid Orbitals

Hybrid orbitals are formed when atomic orbitals mix within the same atom. This occurs during bond formation, often involving the mixing of one s orbital and several p orbitals from the same atom, leading to sp, sp², or sp³ hybrid orbitals. Hybridization allows atoms to form bonds with specific orientations, which is essential for the geometry of molecules.

• Hybrid orbitals are formed from orbitals of the same atom.
• They help define the shape and angles between bonds in a molecule.
• Examples include linear (sp), trigonal planar (sp²), and tetrahedral (sp³) geometries.

These orbitals are crucial for understanding molecular structure and the directional nature of bonds.

Nonbonding Electron Pairs

Nonbonding electron pairs, or lone pairs, are pairs of valence electrons that are not involved in chemical bonding. These electrons can occupy hybrid orbitals, influencing the shape and properties of molecules. In a molecule such as ammonia ( H₃), the nitrogen atom has a lone pair in an sp³ hybrid orbital, affecting the molecular geometry and leading to a trigonal pyramidal shape.

• Lone pairs can occupy hybrid orbitals.
• They are not shared and do not contribute to bonding but affect molecular shape.
• Lone pairs increase electron repulsion forces, influencing the bond angles around the central atom.

Recognizing the role of nonbonding pairs helps clarify molecular geometry and the physical and chemical behavior of compounds.