Which one of the following is an s-block element?

Options

A. Aluminium
B. Chromium
C. Niobium
D. Potassium

Answer

To determine which of the given options is an s-block element, we can follow these steps:

### Step 1: Understand the Structure of the Periodic Table
The periodic table is divided into blocks based on the electron configuration of the elements. The blocks are:
- **s-block**: Groups 1 and 2 (and Helium)
- **p-block**: Groups 13 to 18
- **d-block**: Transition metals (Groups 3 to 12)
- **f-block**: Lanthanides and actinides

### Step 2: Identify the Elements
We need to identify the elements provided in the question. Let's consider the elements mentioned in the video transcript:
- Aluminium (Al)
- Chromium (Cr)
- Niobium (Nb)
- Potassium (K)

### Step 3: Determine the Electron Configuration
Next, we will write the electron configurations for each element to identify their blocks.

1. **Aluminium (Al)**: Atomic number 13
- Electron configuration: 1s² 2s² 2p⁶ 3s² 3p¹
- The outermost electrons are in the 3p subshell, so Al is a **p-block** element.

2. **Chromium (Cr)**: Atomic number 24
- Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
- The outermost electrons are in the 4s and 3d subshells, so Cr is a **d-block** element.

3. **Niobium (Nb)**: Atomic number 41
- Electron configuration: [Kr] 5s² 4d⁴
- The outermost electrons are in the 5s and 4d subshells, so Nb is also a **d-block** element.

4. **Potassium (K)**: Atomic number 19
- Electron configuration: [Ar] 4s¹
- The outermost electron is in the 4s subshell, so K is an **s-block** element.

### Step 4: Conclusion
Among the given elements, **Potassium (K)** is the only s-block element.

### Final Answer
**Potassium (K)** is the s-block element.

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