Question

An element $X$ has $7$ electrons in its L shell. What is true about the element $X$?

• A. It belongs to period $9$ of modern periodic table.
  
• B. Its atom contains $9$ protons.
  
• C. It has a valency of $7$.
  
• D. It can accept an electron to acquire noble gas configuration.
  

Answer 1

Answer: (B), (D)

It can accept an electron to acquire noble gas configuration.
Its atom contains $9$ protons.

If the number of electrons in the $L$ shell of $X$ is $7$, then its atomic number is $9$ (as $2$ electrons are in the $K$ shell and $7$ electrons are in $L$ shell).

Thus, the number of protons in $X$ is $9$ (equal to a number of electrons).

It can acquire a noble gas configuration by accepting one electron to complete its octet as it has $7$ valence electrons.

Hence, option $B$ and $D$ are correct.