Question

Regarding hybridisation which is incorrect? (1) \(\mathrm{BF}_{3}, \mathrm{C}_{2} \mathrm{H}_{4}, \mathrm{C}_{6} \mathrm{H}_{6}\) involves sp \(^{2}\) hybridisation. (2) \(\mathrm{BeF}_{2}, \mathrm{C}_{2} \mathrm{H}_{2}, \mathrm{CO}_{2}\) involves sp hybridisation. (3) \(\mathrm{NH}_{3}, \mathrm{H}_{2} \mathrm{O}, \mathrm{CCl}_{4}\) involves sp \(^{3}\) hybridisation. (4) \(\mathrm{CH}_{4}, \mathrm{C}_{2} \mathrm{H}_{4}, \mathrm{C}_{2} \mathrm{H}_{2}\) involves \(\mathrm{sp}^{2}\) hyoridisation.

Short answer

Fourth statement is incorrect.

Step-by-step solution

- Analyze First Statement

The first statement mentions \(\mathrm{BF}_{3}, \mathrm{C}_{2} \mathrm{H}_{4}, \mathrm{C}_{6} \mathrm{H}_{6}\). \(\mathrm{BF}_{3}\), \(\mathrm{C}_{2} \mathrm{H}_{4}\) and \(\mathrm{C}_{6} \mathrm{H}_{6}\) are all molecules that involve \(\mathrm{sp}^{2}\) hybridisation.

- Analyze Second Statement

The second statement mentions \(\mathrm{BeF}_{2}, \mathrm{C}_{2} \mathrm{H}_{2}, \mathrm{CO}_{2}\). \(\mathrm{BeF}_{2}\), \(\mathrm{C}_{2} \mathrm{H}_{2}\), and \(\mathrm{CO}_{2}\) are all molecules that involve \(\mathrm{sp}\) hybridisation.

- Analyze Third Statement

The third statement mentions \(\mathrm{NH}_{3}, \mathrm{H}_{2} \mathrm{O}, \mathrm{CCl}_{4}\). \(\mathrm{NH}_{3}\), \(\mathrm{H}_{2} \mathrm{O}\), and \(\mathrm{CCl}_{4}\) are all found to involve \(\mathrm{sp}^{3}\) hybridisation.

- Analyze Fourth Statement

The fourth statement mentions \(\mathrm{CH}_{4}, \mathrm{C}_{2} \mathrm{H}_{4}, \mathrm{C}_{2} \mathrm{H}_{2}\). Checking these molecules: \(\mathrm{CH}_{4}\) involves \(\mathrm{sp}^{3}\) hybridisation, \(\mathrm{C}_{2} \mathrm{H}_{4}\) involves \(\mathrm{sp}^{2}\) hybridisation, and \(\mathrm{C}_{2} \mathrm{H}_{2}\) involves \(\mathrm{sp}\) hybridisation. Thus, this combination is incorrect since \(\mathrm{CH}_{4}\) does not involve \(\mathrm{sp}^{2}\) hybridisation.

Key concepts

sp2 hybridisation

In chemistry, sp² hybridisation occurs when one s orbital mixes with two p orbitals, resulting in three equivalent hybrid orbitals. These orbitals form a trigonal planar shape, with 120-degree bond angles.
Some examples of molecules that exhibit sp² hybridisation include:

• Boron trifluoride (BF₃)
• Ethylene (C₂H₄)
• Benzene (C₆H₆)

In these molecules, all atoms are arranged in a planar configuration, and the bond angles reflect the typical 120 degrees associated with sp² hybridisation.

sp hybridisation

sp hybridisation happens when one s orbital combines with one p orbital, leading to two linear hybrid orbitals oriented 180 degrees apart.
This type of hybridisation is often seen in molecules with triple bonds or in molecules requiring linear geometry. Examples include:

• Beryllium fluoride (BeF₂)
• Acetylene (C₂H₂)
• Carbon dioxide (CO₂)

Each of these molecules has a linear shape and bond angles of 180 degrees, which characterize sp hybridisation.

sp3 hybridisation

sp³ hybridisation arises when one s orbital mixes with three p orbitals, resulting in four equivalent hybrid orbitals. These orbitals form a tetrahedral shape with bond angles of 109.5 degrees.
Common examples of molecules with sp³ hybridisation include:

• Methane (CH₄)
• Ammonia (NH₃)
• Water (H₂O)
• Carbon tetrachloride (CCl₄)

In these molecules, the atoms are arranged in a tetrahedral geometry, which allows for the maximum separation of their electron pairs.

molecular geometry

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. It is determined by the types of bonding between atoms (single, double, or triple bonds) and the lone pairs of electrons present.
The most common molecular geometries include:

• Linear: Found in sp-hybridised molecules like CO₂ and C₂H₂.
• Trigonal planar: Common in sp²-hybridised molecules like BF₃ and C₂H₄.
• Tetrahedral: Found in sp³-hybridised molecules like CH₄ and CCl₄.
• Trigonal pyramidal: seen in molecules like NH₃ where there is one lone pair of electrons.
• Bent: seen in molecules like H₂O

Understanding molecular geometry is essential for predicting the behavior, reactivity, and properties of molecules in various chemical reactions.