Coordination Compounds Online Mock Test Class 12 Chemistry – NEET & JEE

Answer: Introduction: Spin-only magnetic moment is the magnetic moment of a coordination compound that arises due to the net spin of the unpaired electrons present in the d-orbitals of the central metal ion. Explanation: The spin-only magnetic moment of a coordination compound can be calculated using the following formula: µS = √n(n+2)BM where, n is the number of unpaired electrons and BM is the Bohr magneton. (a) d⅝5 (in strong ligand field): The number of unpaired electrons in d⅝5 is 5. In strong ligand field, the pairing of electrons takes place and hence, the number of unpaired electrons decreases. Therefore, the spin-only magnetic moment of d⅝5 in strong ligand field will be less than 2.84 BM. Hence, option (a) is not correct. (b) d³ (in weak as well as in strong fields): The number of unpaired electrons in d³ is 3. The spin-only magnetic moment of d³ in weak field is given by: µS = √3(3+2)BM = 3.87 BM In strong field, the pairing of electrons takes place and hence, the number of unpaired electrons decreases. Therefore, the spin-only magnetic moment of d³ in strong ligand field will be less than 3.87 BM. Hence, option (b) is not correct. (c) d⁴ (in weak ligand fields): The number of unpaired electrons in d⁴ is 2. The spin-only magnetic moment of d⁴ in weak field is given by: µS = √2(2+2)BM = 2.83 BM This value is close to 2.84 BM. Therefore, option (c) can be considered as correct. (d) d⁴ (in strong ligand fields): In strong ligand field, the pairing of electrons takes place and hence, the number of unpaired electrons decreases. Therefore, the spin-only magnetic moment of d⁴ in strong ligand field will be less than 2.83 BM. Hence, option (d) is not correct. Conclusion: Hence, the correct option is (c) d⁴ (in weak ligand fields).

In coordination compounds, the primary valency is the number of negative ions that are equivalent to the charge on the metal ion, while the secondary valency is the number of ligands attached to the metal ion:

Primary valency
Definition: The number of negative ions equivalent to the charge on the metal ion
Value: Usually a positive value, but can be zero
Satisfaction: Only satisfied by negatively charged ligands
Directionality: Non-directional
Notation: Dotted lines

Secondary valency
Definition: The number of ligands attached to the metal ion
Satisfaction: Can be satisfied by a neutral molecule, a negatively charged species, or a positively charged species
Directionality: Directional
Notation: Dark or straight lines

The coordination number of cobalt in $C{o}^3+$ will be '6' Siince the given compound gives 3 ions when dissolved in water , its structural formula should be $\left[Cocl{\left(NH3\right)}_3\right]C{l}_2$
$\left[CoCl{\left(Nh3\right)}_3\right]C{l}_2={\left[CoCl{}_3\right]}^2++2C{l}^{-}$
therefroe , only one chlorine atom satisfies both primary and secondary valency of $C{o}^{\mathrm{3+}}$.

(a) Primary valency- This is ionizable and is satisfied by the negative charges. In werner coordination theory the primary valency corresponds to the oxidation state of the central transition metal ion and it is always preferred to satisfied by the negative charged ions . On the other hand the secondary valency corresponds to the coordination number of the metal complex.

The co-ordination number of a central metal atom in a complex is determined by the number of ligands around a metal ion bonded by sigma bonds. It is also define as the number of atoms, ions, or molecules that a central atom or ion holds as its nearest neighbors in a complex.

Answer: b

Explanation: The VSEPR Theory uses electron pairs in atoms to explain the structure of particular molecules. The theories VBT, CFT, LFT, and MOT explain the nature of bonding in coordination compounds.