Find the no of species where dz2 orbital participate in hybridization I3 ,pcl5,lf7,nh4 ,ch4,CO2,xef4

Let's examine each of the given species to determine if the central atom's hybridization involves the dz2 orbital. Keep in mind that d orbital participation in hybridization typically occurs for central atoms from the third period onwards, as they have accessible d orbitals.

First, consider I3−. The central iodine atom has a steric number of 5 (2 bond pairs and 3 lone pairs), leading to a linear shape due to sp3d hybridization. This sp3d hybridization involves one d orbital, and conventionally, this is considered to be the dz2 orbital.

Next is PCl5. The central phosphorus atom has a steric number of 5 (5 bond pairs and 0 lone pairs), resulting in a trigonal bipyramidal geometry with sp3d hybridization. Similar to I3−, this hybridization includes one d orbital, often taken as the dz2.

For IF7, the central iodine atom has a steric number of 7 (7 bond pairs and 0 lone pairs), leading to a pentagonal bipyramidal geometry with sp3d3 hybridization. This hybridization involves three d orbitals, including the dz2 orbital along with dx2−y2 and one other d orbital (dxy or dxz or dyz).

Now consider NH4+. The central nitrogen atom is from the second period and has a steric number of 4 (4 bond pairs and 0 lone pairs), resulting in a tetrahedral geometry with sp3 hybridization. Second-period elements typically do not involve d orbitals in hybridization due to their high energy. Therefore, dz2 does not participate here.

For CH4, the central carbon atom is also from the second period and has a steric number of 4 (4 bond pairs and 0 lone pairs), leading to a tetrahedral geometry with sp3 hybridization. Again, no d orbital, including dz2, participates in this hybridization.

In CO2, the central carbon atom has a steric number of 2 (2 double bonds and 0 lone pairs), resulting in a linear geometry with sp hybridization. No d orbitals are involved in sp hybridization, especially for a second-period element like carbon.

Finally, consider XeF4. The central xenon atom is from the fifth period and has a steric number of 6 (4 bond pairs and 2 lone pairs), resulting in a square planar geometry with sp3d2 hybridization. This hybridization involves two d orbitals, which are typically considered to be dz2 and dx2−y2. Thus, dz2 participates in the hybridization of XeF4.

In summary, the species where the dz2 orbital participates in hybridization are I3−, PCl5, IF7, and XeF4. Therefore, there are 4 such species.