Question

An atom of X forms an ion according to the equation ( X + 2e^- X^2- ). The atomic number of the atom X is:

• A. 16
• B. 10
• C. 12
• D. 14

Hint:

Atoms in Group 16 (Chalcogens) always form (2-) ions, while atoms in Group 2 (Alkaline Earth Metals) always form (2+) ions.

Answer 1

The Correct Option is A

Step 1: Understanding Ion Formation: 
The equation (X X^2-) implies that the atom X accepts 2 electrons to form a negatively charged ion (anion). 

Step 2: Applying the Octet Rule: 
Non-metals gain electrons to complete their valence shell (usually reaching 8 electrons). An atom that gains 2 electrons must have had 6 valence electrons in its neutral state. 

Step 3: Checking the Atomic Numbers: 
16 (Sulphur): 2, 8, 6. (Needs 2 electrons to become 2, 8, 8). Matches. 10 (Neon): 2, 8. (Noble gas, stable). 12 (Magnesium): 2, 8, 2. (Loses 2 electrons to form (Mg^2+)). 14 (Silicon): 2, 8, 4. (Usually forms covalent bonds). 

Step 4: Final Answer: 
The atomic number is 16.