Question

Which of the following is not tetrahedral
A. \[SCl_4\]
B. \[SO_4^{2 - }\]
C. \[Ni(CO)_4\]
D. \[Ni(Cl)_4^{2-}\]

Answer 1

Hint: In a tetrahedral geometry, a central atom is at the center with four atoms that are found at the corners of a tetrahedron.
The bond angles are \[109.5^\circ \]when all four substituents are identical such as methane.

Complete step by step solution:Here in this question, we have to find out which molecule does not have a tetrahedral structure.
A. \[SCl_4\]
S is the central atom here. It has 6 electrons in its valence shell.
Four electrons are involved in bond formation.
The other two electrons form a lone pair.
So, there are four bond pairs and one lone pair.
It has a see-saw structure.
So A is correct.

B. \[SO_4^{2 - }\]
S is the central atom here. It has 4 electrons in its valence shell.
Four electrons are involved in bond formation.
So, there are four bond pairs.
It has a tetrahedral structure.
So, B is incorrect.

C. \[Ni(CO)_4\]
It is a complex compound.
Ni has no charge in this molecule.
So, the total no.of electrons on the central metal atom is 10.
8 electrons lie in the 3d orbital and 2 in the 4s orbital of the central metal.
Here CO is a strong field ligand. So, it, therefore, will pair up the unpaired electrons of the 3d orbital and push two electrons from the 4s orbital to the 3d orbital.
So, the one 4s and three 4p orbitals hybridize to form four \[sp_3\] hybrid orbitals.
These hybrid orbitals accommodate four pairs of electrons from chloride ions.
So, they have tetrahedral geometry.
So, C is incorrect.

D. \[Ni(Cl)_4^{2-}\]
It is a complex compound.
Ni has a +2 charge in this compound.
So, the total no.of electrons on the central metal atom is 8.
All these electrons lie in the 3d of the central metal.
Here \[C{l^ - }\] is a weak field ligand. So, it, therefore, will not pair up the unpaired electrons of the 3d orbital.
So, the one 4s and three 4p orbitals hybridize to form four \[sp_3\] hybrid orbitals.
These hybrid orbitals accommodate four pairs of electrons from chloride ions.
So, they have tetrahedral geometry.
So, D is incorrect.

So, option A is correct.

Note: Complex compound is a kind of compound created by the combination of a central metal atom with non-metal atoms or ions or ligands bonded by covalent, ionic, or co-ordinate bonds.
Werner’s theory is utilized for the prediction of the structure of complex compounds.