Correct answer: \(Na_2O\)
Explanation:
The valency of sodium (Na) is 1, meaning each sodium atom can donate 1 electron.
The valency of oxygen (O) is 2, meaning each oxygen atom needs 2 electrons to complete its octet.
To balance the charges, 2 sodium atoms (each donating 1 electron) are needed to bond with 1 oxygen atom (which needs 2 electrons).
Hence, the correct chemical formula is: \(Na_2O\).
Number of valence electrons in \(Cl^–\) ion are: