Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The first ionization enthalpy of 3d series elements is more than that of group 2 metals
Reason (R) : In 3d series of elements successive filling of d-orbitals takes place.
In the light of the above statements, choose the correct answer from the options given below :

Options

A. Both (A) and (R) are true and (R) is the correct explanation of (A)
B. (A) is true but (R) is false
C. (A) is false but (R) is true
D. Both (A) and (R) are true but (R) is not the correct explanation of (A)

Answer

To solve the question, we will analyze both the Assertion (A) and Reason (R) statements provided.

### Step 1: Understand the Assertion (A)
The assertion states that "The first ionization enthalpy of 3d series elements is more than that of group 2 metals."

- **Ionization enthalpy** is defined as the energy required to remove the outermost electron from an atom in the gaseous state.
- Group 2 metals (alkaline earth metals) have their outermost electrons in the s-orbital, while the 3d series elements have their outermost electrons in the d-orbitals.

### Step 2: Compare Ionization Energies
To compare the first ionization enthalpy of 3d series elements with that of group 2 metals, we need to consider the following:

- **Nuclear Charge**: As we move across the 3d series, the nuclear charge increases, which tends to increase the ionization enthalpy.
- **Shielding Effect**: The d-orbitals have a poorer shielding effect compared to s-orbitals. This means that the effective nuclear charge felt by the outermost electrons in the 3d series is higher than that felt by the outermost electrons in group 2 metals.

### Step 3: Understand the Reason (R)
The reason states that "In 3d series of elements, successive filling of d-orbitals takes place."

- This statement is true. As we move across the transition metals in the 3d series, electrons are added to the d-orbitals.
- The filling of d-orbitals contributes to the overall electron configuration and affects the ionization enthalpy.

### Step 4: Conclusion
Both the assertion and reason are correct. The reason provided correctly explains why the first ionization enthalpy of 3d series elements is greater than that of group 2 metals.

### Final Answer
Both Assertion (A) and Reason (R) are correct, and the reason is the correct explanation for the assertion.