Which one of the following is a 'd-block element' ?

Options

A. Gd
B. Hs
C. Es
D. Cs

Answer

To determine which element is a 'd-block element', we need to understand the characteristics of d-block elements and analyze the given options. Here’s a step-by-step solution:

### Step 1: Understand the Definition of d-block Elements
d-block elements are those elements in which the last electron enters the d-subshell. These elements are found in groups 3 to 12 of the periodic table and typically have incompletely filled d-orbitals in their ground state.

### Step 2: Identify the Given Element
The element in question is Hesium (Hs), which has the atomic number 108.

### Step 3: Determine the Electronic Configuration
The electronic configuration of Hesium is given as:
- Radon (Rn) core: [Rn]
- 5f subshell: 5f^14
- 6d subshell: 6d^6
- 7s subshell: 7s^2

So, the complete electronic configuration is:
\[ \text{[Rn]} 5f^{14} 6d^6 7s^2 \]

### Step 4: Analyze the Last Electron
In the electronic configuration of Hesium, the last electron enters the 6d subshell. Since the d-orbital is being filled, this confirms that Hesium is indeed a d-block element.

### Step 5: Conclusion
Since the last electron of Hesium (Hs) goes into the d-orbital, we conclude that Hesium is a d-block element.

### Final Answer
The correct answer is option B: Hesium (Hs) is a d-block element.

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