Number of the following elements which are p-block elements
Pb, Al, B,K,S,Cd, Zn,Th,Sr

Answer

To determine the number of p-block elements among the given list of elements (Pb, Al, B, K, S, Cd, Zn, Th, Sr), we need to analyze the electronic configurations of each element and identify which ones have their last electron entering the p-subshell.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements provided are:
- Pb (Lead)
- Al (Aluminium)
- B (Boron)
- K (Potassium)
- S (Sulphur)
- Cd (Cadmium)
- Zn (Zinc)
- Th (Thorium)
- Sr (Strontium)

2. **Determine the Atomic Numbers**:
- Pb: 82
- Al: 13
- B: 5
- K: 19
- S: 16
- Cd: 48
- Zn: 30
- Th: 90
- Sr: 38

3. **Write the Electronic Configurations**:
- Pb: [Xe] 6s² 6p²
- Al: [Ne] 3s² 3p¹
- B: [He] 2s² 2p¹
- K: [Ar] 4s¹
- S: [Ne] 3s² 3p⁴
- Cd: [Kr] 4d¹⁰ 5s²
- Zn: [Ar] 3d¹⁰ 4s²
- Th: [Rn] 6d² 7s²
- Sr: [Kr] 5s²

4. **Identify p-block Elements**:
- A p-block element is defined as one where the last electron enters the p-subshell.
- Pb: Last electron in 6p² (p-block)
- Al: Last electron in 3p¹ (p-block)
- B: Last electron in 2p¹ (p-block)
- K: Last electron in 4s¹ (not p-block, it's an s-block element)
- S: Last electron in 3p⁴ (p-block)
- Cd: Last electron in 4d¹⁰ (not p-block, it's a d-block element)
- Zn: Last electron in 3d¹⁰ (not p-block, it's a d-block element)
- Th: Last electron in 6d² (not p-block, it's an f-block element)
- Sr: Last electron in 5s² (not p-block, it's an s-block element)

5. **Count the p-block Elements**: The p-block elements identified are:
- Pb, Al, B, and S.
- Total = 4 p-block elements.

### Final Answer:
The number of p-block elements among the given elements is **4**.

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