What is the VSEPR notation for AsF3? AX3 AX3E1 AX3E2 AXE2
The Correct Answer and Explanation is:
The correct VSEPR notation for arsenic trifluoride (AsF₃) is AX₃E₁.
To determine this notation, we consider the number of bonding pairs and lone pairs around the central atom, arsenic (As). Arsenic belongs to Group 15 of the periodic table, meaning it has five valence electrons. In AsF₃, three of these valence electrons form bonds with fluorine atoms, leaving two electrons as a lone pair on arsenic.
VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron pairs will position themselves to minimize repulsion. The notation AX₃E₁ breaks down as follows. The symbol “A” represents the central atom. The subscript “X₃” indicates three bonded atoms, which in this case are fluorine atoms. The “E₁” denotes the presence of one lone pair on arsenic.
The presence of this lone pair significantly influences the molecular geometry. Lone pairs exert greater repulsion than bonding pairs, which causes a distortion in the structure. Instead of a tetrahedral shape, the molecule adopts a trigonal pyramidal geometry. This occurs because the lone pair pushes the bonded fluorine atoms closer together.
The bond angles in AsF₃ are slightly less than the ideal tetrahedral angle of 109.5 degrees. The lone pair repels the bonded atoms, leading to a bond angle near 97 degrees. This molecular shape affects properties such as dipole moment and reactivity.
In summary, arsenic trifluoride follows AX₃E₁ notation, leading to a trigonal pyramidal molecular geometry. The lone pair creates an asymmetrical structure, influencing both physical and chemical behavior. VSEPR theory helps predict and rationalize these spatial arrangements in molecules.
