Write the atomic number of the element present in the third period and seventeenth group of the periodic table.

Explanation

To find the atomic number of the element present in the third period and seventeenth group of the periodic table, we can follow these steps:

### Step 1: Identify the Period and Group
- The question specifies the third period and the seventeenth group of the periodic table.

### Step 2: Understand the Period
- The third period indicates that the element has three electron shells. The electron shells are designated as K, L, and M.
- K shell can hold a maximum of 2 electrons.
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