Which of the following statements are correct about Zn, Cd and Hg?
A. They exhibit high enthalpy of atomization as the d-subshell is full.
B. Zn and Cd do not show variable oxidation state while Hg shows +I and +II.
C. Compounds of Zn, Cd and Hg are paramagnetic in nature.
D. Zn, Cd and Hg are called soft metals.
Choose the most appropriate from the options given below:
A. They exhibit high enthalpy of atomization as the d-subshell is full.
B. Zn and Cd do not show variable oxidation state while Hg shows +I and +II.
C. Compounds of Zn, Cd and Hg are paramagnetic in nature.
D. Zn, Cd and Hg are called soft metals.
Choose the most appropriate from the options given below:
- B, D only
- B, C only
- A, D only
- C, D only
The Correct Option is A
Approach Solution - 1
To determine which statements about Zn, Cd, and Hg are correct, let's evaluate each option provided:
- High Enthalpy of Atomization: Statement A suggests that Zn, Cd, and Hg exhibit high enthalpy of atomization because the d-subshell is full. The enthalpy of atomization is generally high when atoms form strong metallic bonds. However, as Zn, Cd, and Hg have completely filled d-subshells and are in the d-block but behave more like s-block elements (due to their filled d and s subshells), they have lower enthalpy of atomization than typical transition metals. Thus, this statement is incorrect.
- Oxidation States: Statement B says Zn and Cd do not show variable oxidation states, while Hg shows +I and +II. Zn and Cd typically only exhibit a +II oxidation state due to the stability of their filled d and s orbitals. Mercury can have oxidation states of +I and +II due to its ability to form covalent bonds. This makes statement B correct.
- Paramagnetic Compounds: Statement C claims that compounds of Zn, Cd, and Hg are paramagnetic. Compounds of Zn, Cd, and Hg are typically diamagnetic, as Zn2+, Cd2+, and Hg2+ ions have fully filled d-subshells, rendering them non-paramagnetic. Hence, this statement is incorrect.
- Soft Metals: Statement D states that Zn, Cd, and Hg are called soft metals. Indeed, these metals are considered soft, with mercury being a liquid at room temperature. This makes the statement D correct.
Considering the evaluation:
- Statement B is correct, as it describes the oxidation characteristics of Zn, Cd, and Hg accurately.
- Statement D is also correct, categorizing these elements as soft metals.
Therefore, the correct answer is: B, D only.
Approach Solution -2
- (A) Incorrect. Zn, Cd, and Hg exhibit lower enthalpy of atomization compared to other transition metals in their respective series because they have fully filled d-subshells, which make their bonding weaker.
- (B) Correct. Zn and Cd do not show variable oxidation states, generally remaining in the \( +2 \) state. Hg, however, can show \( +1 \) and \( +2 \) oxidation states due to its unique electron configuration.
- (C) Incorrect. Compounds of Zn, Cd, and Hg are typically diamagnetic because they have fully filled d-orbitals, which do not contribute to unpaired electrons.
- (D) Correct. Zn, Cd, and Hg are known as soft metals due to their malleability and ductility.
The Correct Answer is: B, D only
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