Question

If $N_A$ is the Avogadro's number then number of valence electrons in 4.8 g of $O^{2-}$ is:

• A. $2.4N_A$
• B. $4.2N_A$
• C. $1.6N_A$
• D. $3.2N_A$

Answer 1

Answer: (A)

$2.4N_A$

Number of mole in 4.8 gm of oxygen atom $=\frac{4.8}{16}=0.3$ mole

Number of the valence electron in one ion of $O^{2-}=8$

Number of the valence electron in 0.3 mole of $O^{2-}=8\times 0.3\times N_A=2.4N_A$

Hence, the correct option is $\left(A\right)$.