Problem 51 - Chemistry The Central Science In Si Units

Question

Indicate the hybridization of the central atom in (a) \(\mathrm{H}_{2} \mathrm{~S}\), (b) \(\mathrm{SeF}_{6}\) (c) \(\mathrm{P}(\mathrm{OH})_{3},\) (d) \(\mathrm{AlI}_{3} .\)

Step-by-Step Solution

Answer

(a) sp3, (b) sp3d2, (c) sp3, (d) sp2.

Step 1: Analyze the Central Atom

Identify the central atom for each compound: (a) Sulfur in H2S, (b) Selenium in SeF6, (c) Phosphorus in P(OH)3, (d) Aluminum in AlI3.

Step 2: Determine Electron Groups Around the Central Atom

Count the number of bonded atoms and lone pairs around the central atom for each molecule: (a) In H2S, sulfur has 2 bonds and 2 lone pairs, totaling 4 electron groups. (b) In SeF6, selenium has 6 bonds and 0 lone pairs, totaling 6 electron groups. (c) In P(OH)3, phosphorus has 3 bonds and 1 lone pair, totaling 4 electron groups. (d) In AlI3, aluminum has 3 bonds and 0 lone pairs, totaling 3 electron groups.

Step 3: Assign Hybridization Based on Electron Groups

Use the total number of electron groups to determine hybridization: (a) For 4 electron groups (H2S), the hybridization is sp3. (b) For 6 electron groups (SeF6), the hybridization is sp3d2. (c) For 4 electron groups (P(OH)3), the hybridization is sp3. (d) For 3 electron groups (AlI3), the hybridization is sp2.

Key Concepts

Central Atom

In molecular structures, the central atom plays a crucial role in determining the shape and hybridization of the molecule. The central atom is typically the one with the lowest electronegativity and is often capable of forming multiple bonds. It is the atom around which other atoms or groups are arranged.
For the given compounds:

• In \(\mathrm{H}_{2}\mathrm{S}\), sulfur (S) is the central atom.
• In \(\mathrm{SeF}_{6}\), selenium (Se) is the central atom.
• In \(\mathrm{P(OH)}_{3}\), phosphorus (P) is the central atom.
• In \(\mathrm{AlI}_{3}\), aluminum (Al) is the central atom.

Generally, the central atom is proficient in accepting and sharing electrons, allowing it to accommodate various electron groups like bonded atoms and lone pairs.

Electron Groups

Electron groups around a central atom are crucial for determining hybridization. The concept of electron groups includes both bonded atoms and lone pairs.
Electron groups are:

• Bonded atoms, which are counted as one electron group each.
• Lone pairs, which also count as one electron group each.

Let's explore the electron groups in each molecule:

• In \(\mathrm{H}_{2}\mathrm{S}\), sulfur has 4 electron groups (2 bonded atoms and 2 lone pairs).
• In \(\mathrm{SeF}_{6}\), selenium has 6 electron groups (6 bonded atoms and no lone pairs).
• In \(\mathrm{P(OH)}_{3}\), phosphorus has 4 electron groups (3 bonded atoms and 1 lone pair).
• In \(\mathrm{AlI}_{3}\), aluminum has 3 electron groups (3 bonded atoms and no lone pairs).

Recognizing the count of electron groups helps in accurately determining the hybridization of the central atom.

Bonded Atoms

Bonded atoms refer to the atoms that are directly linked to the central atom in a molecule. In the context of hybridization, each bonded atom contributes an electron group.
For the molecules:

• In \(\mathrm{H}_{2}\mathrm{S}\), sulfur is bonded to 2 hydrogen atoms.
• In \(\mathrm{SeF}_{6}\), selenium is bonded to 6 fluorine atoms.
• In \(\mathrm{P(OH)}_{3}\), phosphorus is bonded to 3 hydroxyl (OH) groups.
• In \(\mathrm{AlI}_{3}\), aluminum is bonded to 3 iodine atoms.

These bonded atoms form the actual bonds around the central atom, whether they are single, double, or triple bonds. The nature and number of these bonded atoms help define the molecular geometry and hybridization state.

Lone Pairs

Lone pairs consist of electrons that do not participate in bonding, yet they occupy space around the central atom. These lone pairs count as individual electron groups and play a significant role in determining hybridization and molecular shape.
In our examples:

• In \(\mathrm{H}_{2}\mathrm{S}\), sulfur possesses 2 lone pairs.
• In \(\mathrm{SeF}_{6}\), selenium has no lone pairs.
• In \(\mathrm{P(OH)}_{3}\), phosphorus comprises 1 lone pair.
• In \(\mathrm{AlI}_{3}\), aluminum has no lone pairs.

Lone pairs often occupy more space than bonded pairs, influencing the shape and angles within a molecule. Considering lone pairs is essential for understanding the complete hybrization and spatial orientation of molecules.