Question

The electrons, identified by quantum numbers $n$ and $l$,
$\left(i\right)n=4,l=1,\left(ii\right)n=4,l=0,\left(iii\right)n=3,l=2,\left(iv\right)n=3,l=1$ can be placed in order of increasing energy, from the lowest to highest, as:

• A. $\left(iv\right)<\left(ii\right)<\left(iii\right)<\left(i\right)$
• B. $\left(ii\right)<\left(iv\right)<\left(i\right)<\left(iii\right)$
• C. $\left(i\right)<\left(iii\right)<\left(ii\right)<\left(iv\right)$
• D. $\left(iii\right)<\left(i\right)<\left(iv\right)<\left(ii\right)$

Answer 1

The correct option is A $\left(iv\right)<\left(ii\right)<\left(iii\right)<\left(i\right)$

$\left(i\right)n=4,l=1\to 4p-orbital\left(ii\right)n=4,l=0\to 4s-orbital\left(iii\right)n=3,l=2\to 3d-orbital\left(iv\right)n=3,l=1\to 3d-orbital$
Energy can be calculated by $n+l$ rule
According to Aufbau principle, energies of above mentioned orbitals are in the order of
$\left(iv\right)3p<\left(ii\right)4s<\left(iii\right)3d<\left(i\right)4p$