What is the electronic configuration of the element in the third period which gains one electron to change into an anion?

Explanation

To find the electronic configuration of the element in the third period that gains one electron to form an anion, we can follow these steps:

### Step 1: Identify the Period and Group
The question specifies that we are looking for an element in the third period of the periodic table. The third period contains the elements: Sodium (Na), Magnesium (Mg), Aluminum (Al), Silicon (Si), Phosphorus (P), Sulfur (S), Chlorine (Cl), and Argon (Ar).

### Step 2: Determine Which Element Gains One Electron
We need to find an element that can gain one electron to form an anion. Anions are typically formed by nonmetals, and among the elements in the third period, the halogens (which are nonmetals) are known to gain electrons. The halogens in the third period is Chlorine (Cl).

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