Question

An atom of an element $\left(X\right)$ has its $K$, $L$ and $M$ shells filled with some electrons. It reacts with sodium metal to from a compound $NaX$. The number of electrons in the $M$ shell of the atom $\left(X\right)$ will be:

• A. Eight
• B. Seven
• C. Two
• D. One

Answer 1

The correct option is B Seven

An atom of an element $\left(X\right)$ has its K, L and M shells filled with some electrons. It reacts with sodium metal to from a compound $NaX$. The number of electrons in the M shell of the atom (X) will be Seven.
In $NaX$, Na forms $N{a}^{+}$ and $X$ forms negtive ions. Thus, $X$ gains one electron to form uni negative ion in which octet will be completed. Hence, $X$ has 7 valence electrons
Hence, the option (B) is correct answer.