Total Lone Pairs on Central Atoms of Chemical Species

To find the total number of lone pairs of electrons located on the central atom across each of the given species, we evaluate the valence electron shell configuration for each central atom individually using VSEPR theory principles:

1. $[\text{TeBr}_6]^{2-}$:

   • Central atom: Tellurium ($\text{Te}$, Group 16, $Z = 52$) has $6$ valence electrons.
   • Net charge on the ion: $-2$, which adds $2$ valence electrons to the central atom.
   • Total valence electrons available on $\text{Te} = 6 + 2 = 8$.
   • Number of single bonds formed with six $\text{Br}$ atoms $= 6$ (using $6$ electrons).
   • Remaining unbonded electrons on $\text{Te} = 8 - 6 = 2$ electrons.
   • Number of lone pairs on $\text{Te} = \frac{2}{2} = 1$.

2. $[\text{BrF}_2]^+$:

   • Central atom: Bromine ($\text{Br}$, Group 17, $Z = 35$) has $7$ valence electrons.
   • Net charge on the ion: $+1$, which removes $1$ valence electron from the central atom.
   • Total valence electrons available on $\text{Br} = 7 - 1 = 6$.
   • Number of single bonds formed with two $\text{F}$ atoms $= 2$ (using $2$ electrons).
   • Remaining unbonded electrons on $\text{Br} = 6 - 2 = 4$ electrons.
   • Number of lone pairs on $\text{Br} = \frac{4}{2} = 2$.

3. $\text{SNF}_3$:

   • Central atom: Sulfur ($\text{S}$, Group 16, $Z = 16$) has $6$ valence electrons.
   • Bonding: Sulfur forms a triple bond with Nitrogen ($\text{S}\equiv\text{N}$, using $3$ electrons) and three single bonds with Fluorine atoms ($3 \times \text{S}-\text{F}$, using $3$ electrons).
   • Total electrons used in bonding by $\text{S} = 3 + 3 = 6$.
   • Remaining unbonded electrons on $\text{S} = 6 - 6 = 0$ electrons.
   • Number of lone pairs on $\text{S} = 0$.

4. $[\text{XeF}_3]^-$:

   • Central atom: Xenon ($\text{Xe}$, Group 18, $Z = 54$) has $8$ valence electrons.
   • Net charge on the ion: $-1$, which adds $1$ valence electron to the central atom.
   • Total valence electrons available on $\text{Xe} = 8 + 1 = 9$.
   • Number of single bonds formed with three $\text{F}$ atoms $= 3$ (using $3$ electrons).
   • Remaining unbonded electrons on $\text{Xe} = 9 - 3 = 6$ electrons.
   • Number of lone pairs on $\text{Xe} = \frac{6}{2} = 3$.

Total sum of lone pairs on central atoms: $\text{Total Lone Pairs} = 1 + 2 + 0 + 3 = 6$