The aotmic number of astatine which belongs to six period is

Options

A. 53
B. 54
C. 85
D. 86

Explanation

To find the atomic number of astatine, which belongs to the sixth period of the periodic table, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Group and Period**: Astatine (At) is a member of the halogen group (Group 17) and is located in the sixth period of the periodic table.

2. **List the Halogens**: The halogens in order of increasing atomic number are:
- Fluorine (F) - Atomic number 9
- Chlorine (Cl) - Atomic number 17
- Bromine (Br) - Atomic number 35
- Iodine (I) - Atomic number 53
- Astatine (At) - Atomic number ?

3. **Determine the Pattern**: Notice the pattern in the atomic numbers of the halogens:
- From F to Cl: 17 - 9 = 8
- From Cl to Br: 35 - 17 = 18
- From Br to I: 53 - 35 = 18
- From I to At: The next number can be calculated by adding 32 to 53.

4. **Calculate the Atomic Number of Astatine**:
- Atomic number of Iodine (I) = 53
- Adding 32 (the difference from Iodine to Astatine):
\[ 53 + 32 = 85 \]
- Therefore, the atomic number of Astatine (At) is 85.

5. **Conclusion**: The atomic number of astatine is 85.

### Final Answer:
The atomic number of astatine, which belongs to the sixth period, is **85**.

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