Question

Given below are two statements:
Statement I: The number of species among \( SF_4 \), \( NH_4^+ \), \( [NiCl_4]^{2-} \), \( XeF_4 \), \( [PtCl_4]^{2-} \), \( SeF_4 \) and \( [Ni(CN)_4]^{2-} \), that have tetrahedral geometry is 3.
Statement II: In the set \( [NO_2] \), \( BeH_2 \), \( BF_3 \), \( AlCl_3 \), all the molecules have incomplete octet around the central atom.
In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is false but Statement II is true
• D. Statement I is true but Statement II is false

Hint:

Remember that 4d and 5d transition metals (like Pt) typically form square planar complexes with coordination number 4, regardless of the ligand strength.

Answer 1

The Correct Option is C

Step 1: Evaluation of Statement I (Geometry)

Check the geometry of each given species:

• \(SF_4\): Hybridisation \(sp^3d\), see-saw shape (not tetrahedral).

• \(NH_4^+\): Hybridisation \(sp^3\), tetrahedral.

• \(Ni(CO)_4\): Hybridisation \(sp^3\), tetrahedral.

• \(XeF_4\): Hybridisation \(sp^3d^2\), square planar.

• \([PtCl_4]^{2-}\): Hybridisation \(dsp^2\), square planar.

• \(SeF_4\): Hybridisation \(sp^3d\), see-saw shape.

• \([Ni(CN)_4]^{2-}\): Hybridisation \(dsp^2\), square planar.

Total number of tetrahedral species = 2 (\(NH_4^+\) and \(Ni(CO)_4\)).

Since Statement I claims the number is 3, Statement I is False.

Step 2: Evaluation of Statement II (Octet Rule)

• \(NO\): Total valence electrons = 11 (odd-electron molecule). Nitrogen has an incomplete octet.

• \(BeH_2\): Beryllium forms two bonds and has only 4 electrons around it. Incomplete octet.

• \(BF_3\): Boron forms three bonds and has only 6 electrons. Incomplete octet.

• \(AlCl_3\): Aluminium forms three bonds and has only 6 electrons. Incomplete octet.

All the given species violate the octet rule. Statement II is True.

Final Answer:
Statement I is False and Statement II is True.
Correct option: Option 3.