The energy of orbitals in a hydrogen atom can be determined by which of the following quantum numbers?

$Be$'s $4^{th}$ electron will have four quantum numbers $(n, l, m, s)$:

The Aufbau principle is not satisfied by which of the following pairs of elements?

The representation of the ground state electronic configuration of $He$ by box-diagram as $\uparrow \uparrow$ is wrong because it violates

Explain the Pauli exclusion principle with an example.

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