Question

Which element with lowest atomic number follows rule (b)?

• A. 19${}^k$
• B. 24${}^{Cr}$
• C. 11${}^{Na}$
• D. 29${}^{Cu}$

Answer 1

The correct option is C 11${}^{Na}$

As we know,
2p and 3s both have the same value of n+l but as 2p has a lower value of n so first it will fill and then electron move to 3s.

Thus, the correct option is $\text{C}$