If there are $2$ nodal surfaces in the third excited state,find the orbital angular momentum.

The maximum number of electrons that can be accommodated in the $M$ shell is

The orbital diagram in which the Aufbau principle is violated is:
$2s$ $2p_x$ $2p_y$ $2p_z$

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

In a multielectron atom,which of the following orbitals described by three quantum numbers will have the same energy in the absence of electric and magnetic fields?
$A: n=1, \ell=0, m_{\ell}=0$
$B: n=2, \ell=0, m_{\ell}=0$
$C: n=2, \ell=1, m_{\ell}=1$
$D: n=3, \ell=2, m_{\ell}=1$
$E: n=3, \ell=2, m_{\ell}=0$
Choose the correct answer from the options given below:

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