Which is a chalcogen?

Options

A. Element with atomic no. 8
B. Element with atomic no. 34
C. Element with atomic no. 16
D. All of these

Explanation

To determine which element is a chalcogen, we need to understand what chalcogens are and identify their electronic configurations. Chalcogens belong to Group 16 of the periodic table and include elements such as oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). The defining characteristic of chalcogens is that they have six valence electrons in their outermost shell.

### Step-by-Step Solution:

1. **Identify the Group of Elements**:
Chalcogens are found in Group 16 of the periodic table. The elements in this group include oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po).

2. **Examine the Atomic Numbers**:
We need to look at the atomic numbers provided in the question. Let's analyze the atomic numbers mentioned in the video transcript: 8, 16, and 34.

3. **Determine the Electronic Configurations**:
- For atomic number 8 (Oxygen):
- Electronic configuration: 1s² 2s² 2p⁴, which can be simplified to 2, 6 (2 electrons in the first shell and 6 in the second shell).
- For atomic number 16 (Sulfur):
- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁴, which can be simplified to 2, 8, 6.
- For atomic number 34 (Selenium):
- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴, which can be simplified to 2, 8, 18, 6.

4. **Count the Valence Electrons**:
- Oxygen has 6 valence electrons (2 in the first shell and 6 in the second).
- Sulfur has 6 valence electrons (2 in the first shell, 8 in the second, and 6 in the third).
- Selenium has 6 valence electrons (2 in the first shell, 8 in the second, 18 in the third, and 6 in the fourth).

5. **Conclusion**:
Since all three elements (atomic numbers 8, 16, and 34) have 6 valence electrons, they all belong to the chalcogen group. Therefore, the answer is that all of these elements are chalcogens.

### Final Answer:
All of the elements with atomic numbers 8, 16, and 34 are chalcogens.

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