Question

answer the questions in the table below about the shape of the bromodifluoride (brf₂⁻) anion. how many electron groups are around the central bromine atom? note: one \electron group\ means one lone pair, one single bond, one double bond, or one triple bond. what phrase best describes the arrangement of these electron groups around the central bromine atom? (you may need to use the scrollbar to see all the choices.)

Explanation:

Step1: Calculate valence - electrons of central atom

Bromine (Br) is in Group 7A, so it has 7 valence electrons. Fluorine (F) is also in Group 7A, with 7 valence electrons each. The anion has a - 1 charge. The central Br atom in $BrF_2^-$ has 7 valence electrons, and it forms 2 single bonds with 2 F atoms. The number of non - bonding (lone) pairs on Br can be calculated using the formula: $\text{Lone pairs}=\frac{1}{2}(V - N - C)$, where $V$ is the valence electrons of the central atom, $N$ is the number of non - central atoms, and $C$ is the charge of the ion. Here, $V = 7$, $N=2$ (2 F atoms), and $C=- 1$. So the number of lone pairs on Br is $\frac{1}{2}(7 - 2+1)=3$. The number of bonding pairs is 2. The total number of electron groups around the central Br atom is the sum of bonding and non - bonding pairs, which is $3 + 2=5$.

Step2: Determine electron - group arrangement

According to the VSEPR (Valence - Shell Electron - Pair Repulsion) theory, when there are 5 electron groups around a central atom, the electron - group arrangement is trigonal bipyramidal.

Answer:

How many electron groups are around the central bromine atom? 5
What phrase best describes the arrangement of these electron groups around the central bromine atom? Trigonal bipyramidal