Question

An element has an atomic number $20$. How many electrons will be present in $K,L,M$ and $N$ shells of its atom?

• A. $2,8,6,4$
• B. $2,8,7,3$
• C. $3,7,7,3$
• D. $2,8,8,2$

Answer 1

Answer: (D)

$2,8,8,2$

Calcium with atomic number $20$ will have $2,8,8,2$ electrons in $K,L,M$ and $N$ shells respectively. $K,L,M$ shells can accomodate $2,8,8$ electrons respectively. The remaining 2 electrons will enter $N$ shell.