Question

The shape of \(\mathrm{BF}_{3}\) molecule is

Short answer

Answer: The shape of the BF₃ molecule is trigonal planar.

Step-by-step solution

Identify the central atom

In \(\mathrm{BF}_{3}\), boron (B) is the central atom with three fluorine (F) atoms bonded to it.

Determine the number of valence electrons

First, we need to find the total number of valence electrons in the molecule. Boron has 3 valence electrons while each fluorine atom has 7 valence electrons. So, the total number of valence electrons is: \(3 + 3 \times 7 = 3 + 21 = 24\).

Determine the number of bonding and lone electron pairs

In \(\mathrm{BF}_{3}\), boron forms three single bonds with three fluorine atoms, corresponding to 6 bonding electrons. This leaves 18 electrons, which can be arranged into 9 lone electron pairs—6 of these pairs will be attached to the three fluorine atoms, and the remaining 3 pairs will be assigned to the central boron atom. However, since boron is an exception and can have incomplete octets, it has no lone pairs, and all 9 lone pairs belong to the three fluorine atoms (3 lone pairs each).

Determine the electron pair geometry

Now, we need to determine the electron pair geometry around the central atom, which is the arrangement of all electron pairs (bonding and lone) around the central atom. Boron has three bonding electron pairs and no lone electron pairs, making the electron pair geometry trigonal planar.

Determine the molecular geometry

Since there are no lone electron pairs on the central atom (boron), the molecular geometry is the same as the electron pair geometry. Therefore, the shape of the \(\mathrm{BF}_{3}\) molecule is trigonal planar.

Key concepts

Trigonal Planar

The concept of trigonal planar geometry is central to understanding shapes like that of the \(\mathrm{BF}_3\) molecule. In this arrangement, the molecule is structured in a flat triangle.

• There are three atoms equidistant from one another.
• The bond angles are all fixed at \(120^\circ\), which helps minimize repulsion between the atoms.

This kind of geometry is common when the central atom has three bonding pairs and no lone pairs, as in \(\mathrm{BF}_3\). Because there are no lone pairs, the geometric structure is solely determined by the locations of the bonded atoms. This feature gives \(\mathrm{BF}_3\) its distinct planar shape that is crucial in understanding its chemical properties.

Molecular Geometry

Molecular geometry describes the three-dimensional arrangement of atoms within a molecule. This is influenced by the number and arrangement of electron pairs surrounding the central atom.In the case of \(\mathrm{BF}_3\), the molecular geometry is trigonal planar. With boron as the central atom, surrounded by three fluorine atoms, the geometry matches perfectly with the electron pair geometry due to absence of lone pairs. Here's why this matters:

• Helps predict how molecules interact with each other and with other substances.
• Provides insight into the molecule’s physical properties, like boiling point and polarity.

Understanding molecular geometry is key in fields such as chemistry and pharmacology, as it helps predict the behavior and interaction of molecules.

Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom, crucial for bonding between atoms to form molecules.In a molecule like \(\mathrm{BF}_3\), each boron atom has 3 valence electrons and each fluorine atom has 7.

• These electrons are responsible for forming bonds. In \(\mathrm{BF}_3\), they link boron to fluorine through single bonds.
• The understanding of valence electrons helps determine how atoms will bond and the resulting molecular structure.

Knowing the number of valence electrons is essential for determining the electron pair geometry and predicting the molecule’s behavior. It also helps in calculating the total number of electrons involved in chemical bonding, which is fundamental for understanding how molecules form and maintain their shape.