Question

Which of the following elements have completely filled L- shell?

• A. $\text{Ne}$
• B. $\text{F}$
• C. $\text{Be}$
• D. $\text{Na}$

Answer 1

Answer: (A), (D)

The correct options are
A $\text{Ne}$
D $\text{Na}$

Atomic number of sodium, neon, fluorine and beryllium are 10, 11, 9 and 4 respectively.
By analysing the electronic configuration of sodium (2, 8, 1) and neon (2, 8), we can say that both these elements have 8 electrons in their L-shell which is the maximum that can be accommodated.
Fluorine ($\text{F}$) and beryllium ($\text{Be}$) have only 7 and 2 electrons respectively in their L-shell.
Thus, sodium($\text{Na}$) and neon ($\text{Ne}$) have completely filled L-shell.