What would be the atomic number of the last member of the halogen group?

Options

A. 115
B. 119
C. 117
D. 121

Explanation

To determine the atomic number of the last member of the halogen group, we can follow these steps:

### Step 1: Identify the Halogen Group
The halogens belong to Group 17 of the periodic table. The elements in this group are:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)
- Astatine (At)

### Step 2: List the Atomic Numbers
Next, we will write down the atomic numbers of these halogen elements:
- Fluorine (F) - Atomic number 9
- Chlorine (Cl) - Atomic number 17
- Bromine (Br) - Atomic number 35
- Iodine (I) - Atomic number 53
- Astatine (At) - Atomic number 85

### Step 3: Determine the Pattern
Now, we observe the atomic numbers:
- The atomic numbers increase as we move down the group.
- The difference between the atomic numbers of consecutive halogens is not constant, but we can see that the last known halogen, Astatine, has an atomic number of 85.

### Step 4: Predict the Next Element
The next element after Astatine in the periodic table would be the hypothetical element that follows the trend of the halogens. We can predict its atomic number by observing the differences:
- The difference between Iodine (53) and Astatine (85) is 32.

### Step 5: Calculate the Atomic Number of the Next Halogen
If we assume that the next halogen follows the same pattern, we can add 32 to the atomic number of Astatine (85):
- 85 + 32 = 117

### Conclusion
Thus, the atomic number of the last member of the halogen group is **117**.

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