Question

question 19
what is the electron group arrangement and molecular shape for bf₃?
trigonal planar; t - shaped
tetrahedral; bent
trigonal planar; trigonal planar
tetrahedral; trigonal pyramidal

Explanation:

• Electron group arrangement:
• Boron (\(B\)) in \(BF_3\) has 3 valence electrons. Each \(F\) atom contributes 1 electron for bonding. So, the total number of bonding electron pairs around \(B\) is \(\frac{3 + 3\times1}{2}=3\) (using the formula for electron - pair count around a central atom: \(\text{Electron pairs}=\frac{\text{Valence electrons of central atom}+\text{Number of monovalent surrounding atoms}}{2}\)).
• According to VSEPR (Valence - Shell Electron - Pair Repulsion) theory, when the number of electron groups (\(n = 3\)) around a central atom (with no lone pairs, since \(B\) in \(BF_3\) has no non - bonding electrons), the electron - group arrangement is trigonal planar.
• Molecular shape:
• Since there are no lone pairs on the central \(B\) atom and the number of bonding groups is 3, the molecular shape (which is determined by the arrangement of atoms) is also trigonal planar. In VSEPR, when the number of bonding groups (\(m=3\)) and the number of lone pairs (\(l = 0\)) around a central atom (\(AX_m\) type, where \(A\) is the central atom and \(X\) is the surrounding atom), the molecular geometry is the same as the electron - group geometry.

Answer:

trigonal planar; trigonal planar