Count of Square Planar Species in Given List

To determine the number of species exhibiting a square planar geometry, we analyze the hybridization, steric number, and molecular geometry for each given species:

1. $\text{XeF}_4$:

   • Central atom $\text{Xe}$ has 8 valence electrons.
   • Number of bond pairs ($\text{bp}$) = $4$, Number of lone pairs ($\text{lp}$) = $\frac{8 - 4}{2} = 2$.
   • Steric Number ($\text{SN}$) = $4 + 2 = 6 \implies sp^3d^2$ hybridization.
   • With 2 lone pairs situated in trans-axial positions to minimize repulsions, the molecular shape is square planar.

2. $\text{SF}_4$:

   • Central atom $\text{S}$ has 6 valence electrons.
   • $\text{bp} = 4$, $\text{lp} = \frac{6 - 4}{2} = 1$.
   • $\text{SN} = 4 + 1 = 5 \implies sp^3d$ hybridization.
   • The molecular shape is see-saw.

3. $\text{SiF}_4$:

   • Central atom $\text{Si}$ has 4 valence electrons.
   • $\text{bp} = 4$, $\text{lp} = 0$.
   • $\text{SN} = 4 \implies sp^3$ hybridization.
   • The molecular shape is tetrahedral.

4. $\text{BF}_4^-$:

   • Central atom $\text{B}^-$ has 4 valence electrons.
   • $\text{bp} = 4$, $\text{lp} = 0$.
   • $\text{SN} = 4 \implies sp^3$ hybridization.
   • The molecular shape is tetrahedral.

5. $\text{BrF}_4^-$:

   • Central atom $\text{Br}^-$ has 8 valence electrons.
   • $\text{bp} = 4$, $\text{lp} = \frac{8 - 4}{2} = 2$.
   • $\text{SN} = 4 + 2 = 6 \implies sp^3d^2$ hybridization.
   • With 2 lone pairs in trans positions, the molecular shape is square planar.

6. $[\text{Cu}(\text{NH}_3)_4]^{2+}$:

   • $\text{Cu}^{2+}$ has a $3d^9$ electronic configuration.
   • With the strong-field ligand $\text{NH}_3$, it undergoes $dsp^2$ hybridization (due to Jahn-Teller effect).
   • The coordination geometry is square planar.

7. $[\text{FeCl}_4]^{2-}$:

   • $\text{Fe}^{2+}$ has a $3d^6$ configuration.
   • $\text{Cl}^-$ is a weak-field ligand, giving $sp^3$ hybridization.
   • The coordination geometry is tetrahedral.

8. $[\text{CoCl}_4]^{2-}$:

   • $\text{Co}^{2+}$ has a $3d^7$ configuration.
   • $\text{Cl}^-$ is a weak-field ligand, resulting in $sp^3$ hybridization.
   • The coordination geometry is tetrahedral.

9. $[\text{PtCl}_4]^{2-}$:

   • $\text{Pt}^{2+}$ is a $5d^8$ metal ion.
   • Due to the large crystal field splitting energy ($\Delta_o$) of $5d$ series elements, all 4-coordinate $\text{Pt(II)}$ complexes adopt a low-spin configuration with $dsp^2$ hybridization.
   • The coordination geometry is square planar.

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Conclusion:

The species that possess a square planar geometry are:

1. $\text{XeF}_4$
2. $\text{BrF}_4^-$
3. $[\text{Cu}(\text{NH}_3)_4]^{2+}$
4. $[\text{PtCl}_4]^{2-}$

Total number of square planar species = $4$.