In case of d-block elements

Options

A. outermost and penultimate shells are incomplete
B. both penultimate and pre-penultimate shells are incomplete
C. outermost shell is incomplete
D. innermost shell is incomplete

Answer

To solve the question regarding d-block elements, we need to analyze the characteristics of these elements based on their electron configuration. Let's break down the solution step by step.

### Step 1: Understand d-block Elements
D-block elements are defined as those elements that have their outermost electrons filling the d-orbitals. These elements are typically found in groups 3 to 12 of the periodic table.

**Hint:** Remember that d-block elements correspond to the filling of d-orbitals, which are associated with the penultimate energy level.

### Step 2: Identify Electron Configuration
For d-block elements, the general electron configuration can be represented as:
- (n-1)d^1 to (n-1)d^10 ns^0 to ns^2
Where 'n' is the principal quantum number of the outermost shell.

**Hint:** Focus on the fact that d-block elements have partially filled d-orbitals, which is crucial for their properties.

### Step 3: Analyze the Options
Now, let’s analyze the given options:
1. **Outermost and penultimate cells are incomplete.**
2. **Both penultimate and pre-penultimate cells are incomplete.**
3. **Outermost cell is complete; innermost cell is complete.**

**Hint:** Look for the option that reflects the nature of d-block elements having partially filled orbitals.

### Step 4: Determine the Correct Option
In d-block elements:
- The outermost shell (s-orbital) can have 1 or 2 electrons.
- The penultimate shell (d-orbital) must be partially filled (not fully filled).

Thus, the first option, "Outermost and penultimate cells are incomplete," is correct because both the outermost s-orbital and the penultimate d-orbital can be partially filled.

**Hint:** Consider the definitions of "complete" and "incomplete" in the context of electron configurations.

### Conclusion
The correct answer to the question is:
**Outermost and penultimate cells are incomplete.**