Calculate the hybridisation of B and N in -- NH₃.BF₃ (Dative compound)

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To determine the hybridization of boron (B) and nitrogen (N) in the compound NH3.BF3, we need to analyze the molecular structures of both ammonia (NH3) and boron trifluoride (BF3) individually, as well as how they interact in this dative compound.

Understanding Ammonia (NH3)

In ammonia, nitrogen is the central atom bonded to three hydrogen atoms. To find the hybridization of nitrogen, we can follow these steps:

• Count the Valence Electrons: Nitrogen has five valence electrons, and each hydrogen contributes one, giving a total of 8 electrons.
• Determine the Steric Number: The steric number is the sum of the number of atoms bonded to the central atom and the number of lone pairs. Here, nitrogen is bonded to three hydrogens and has one lone pair, resulting in a steric number of 4.
• Identify the Hybridization: A steric number of 4 corresponds to sp³ hybridization. This means nitrogen's orbitals mix to form four equivalent sp³ hybrid orbitals, which arrange themselves in a tetrahedral geometry.

Examining Boron Trifluoride (BF3)

Boron trifluoride has boron as the central atom bonded to three fluorine atoms. Let's analyze boron's hybridization:

• Count the Valence Electrons: Boron has three valence electrons, and each fluorine contributes seven, totaling 24 electrons. However, in BF3, boron only uses three of its electrons to bond with fluorine.
• Determine the Steric Number: Boron is bonded to three fluorine atoms and has no lone pairs, giving it a steric number of 3.
• Identify the Hybridization: A steric number of 3 indicates sp² hybridization. The three sp² hybrid orbitals arrange themselves in a trigonal planar geometry.

Analyzing the Dative Bond Formation

In the dative compound NH3.BF3, nitrogen donates its lone pair to boron, forming a coordinate bond. This interaction does not change the hybridization of either atom:

• Nitrogen's Hybridization: Remains sp³ due to its original bonding structure in NH3.
• Boron’s Hybridization: Stays as sp² since it does not gain any additional lone pairs or bonds that would alter its steric number.

Final Thoughts

In summary, the hybridization of nitrogen in NH3 is sp³, while boron in BF3 is sp². The formation of the dative bond does not alter these hybridizations but rather illustrates the ability of nitrogen to share its lone pair with boron, enhancing the stability of the compound.