Problem 47 - Chemistry The Central Science

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. (c) To create a hybrid orbital, you could use the sorbital on one atom with a porbital on another atom. (d) Nonbonding electron pairs cannot occupy a hybrid orbital.

Step-by-Step Solution

Answer

(a) False - Greater orbital overlap leads to a stronger bond. (b) True - Greater orbital overlap leads to a shorter bond. (c) False - Hybrid orbitals are formed on the same atom by combining its atomic orbitals. (d) False - Nonbonding electron pairs can occupy hybrid orbitals.

Step 1: Statement (a)

The greater the orbital overlap in a bond, the weaker the bond. This statement is **false**. The greater the orbital overlap in a bond, the stronger the bond. In simple terms, the more overlapping between orbitals leads to a higher electron density between atoms resulting in a stronger attraction between the positively charged nuclei and the electrons, hence, a stronger bond is formed.

Step 2: Statement (b)

The greater the orbital overlap in a bond, the shorter the bond. This statement is **true**. In cases where there is more overlapping, the electron density is higher between the atoms. Due to this increased electron density, the nuclei of both atoms are attracted more, and as a result, the bond length decreases. Hence, a greater orbital overlap leads to a shorter bond.

Step 3: Statement (c)

To create a hybrid orbital, you could use the s-orbital on one atom with a p-orbital on another atom. This statement is **false**. Hybrid orbitals are formed on the same atom by combining its different atomic orbitals, such as s, p, and d orbitals (if available). The creation of hybrid orbitals occurs before the bond formation. However, the mix of atomic orbitals is determined by how many other atoms are bonded to the nucleus of the atom in question. After these hybrid orbitals are formed, they then overlap with orbitals from other atoms to form chemical bonds.

Step 4: Statement (d)

Nonbonding electron pairs cannot occupy a hybrid orbital. This statement is **false**. Nonbonding electron pairs can and do occupy hybrid orbitals. These nonbonding electron pairs are also called lone pairs. In molecules, these lone pairs are located in hybrid orbitals that are not involved in bonding with other atoms. Hence, nonbonding electron pairs can exist in a hybrid orbital.

Key Concepts

Molecular Bonding

Molecular bonding occurs when atoms share or exchange electrons to form molecules. At the heart of molecular bonding is orbital overlap. This is the process where atomic orbitals combine to allow electrons to be shared between atoms.
The more orbital overlap there is, the stronger the bond formed. This is because with greater overlap more electrons are positioned between the positively charged nuclei, thereby increasing the attraction. As a result, the atoms are held together more tightly, strengthening the bond. Another consequence of greater orbital overlap is a shorter bond length. When electron density is highest between atoms, the nuclei are pulled closer together, resulting in a shorter distance between them. Thus, a significant characteristic of strong molecular bonding is the greater overlap that leads to shorter, stronger bonds.

Hybrid Orbitals

Hybrid orbitals are a central concept in the understanding of molecular bonding. They form when atomic orbitals within a single atom mix to create new orbitals that are better suited for bonding.
This mixing involves the s, p, and sometimes d orbitals, rather than combining orbitals from different atoms. The process of hybridization adjusts the orientation and energy levels of the orbitals, making them more effective during bonding. Once hybrid orbitals are formed, they overlap with orbitals from other atoms to create strong chemical bonds. A good example of hybridization is seen in the carbon atom, where one s and three p orbitals combine to form four equivalent sp³ hybrid orbitals. These sp³ orbitals allow for the tetrahedral shape seen in molecules like methane (CH₄).
Hybrid orbitals thus facilitate better alignment and stronger bonds by optimizing the orientation and energy levels of the participating atomic orbitals.

Nonbonding Electron Pairs

Nonbonding electron pairs, also known as lone pairs, are pairs of valence electrons that are not shared between atoms. Despite not partaking in bond formation, these lone pairs still occupy hybrid orbitals in the atom. Lone pairs reside in hybrid orbitals because these are the best positions to minimize repulsion between electron pairs within the same atom. By doing so, they help preserve the geometry and stability of the molecule.
The presence of nonbonding electron pairs can significantly influence the shape and reactivity of a molecule. For instance, in water (H₂O), the two lone pairs on oxygen occupy hybrid orbitals, resulting in a bent molecular shape. Understanding the role of nonbonding electron pairs is crucial in predicting the structure and behavior of molecules. They are an essential aspect of valence shell electron pair repulsion (VSEPR) theory, which helps determine the three-dimensional shape of molecules.