Question

After $np$-orbitals are filled, the next orbital filled will be:

• A. $(n+1)s$
• B. $(n+2)p$
• C. $(n+1)d$
• D. $(n+2)s$

Answer 1

The correct option is A $(n+1)s$

After np-orbitals are filled, the next orbital filled will be $(n+1)s$.
According to Aufbau principle, orbitals are filled in order of increasing value of $(n+l)$.
If two orbitals have same value of $(n+l)$, then the orbital with lower value of n will be filled first.
For np orbital, $(n+l)=(n+1)$
For $(n+1)s$ orbital, $(n+l)=(n+1+0)=(n+1)$
For $(n+2)p$ orbital, $(n+l)=(n+2+1)=(n+3)$
For $(n+1)d$ orbital, $(n+l)=(n+1+2)=(n+3)$
For $(n+2)s$ orbital, $(n+l)=(n+2+0)=(n+2)$