How many nodal (angular) planes are present in the $d_{xy}$ orbital? Which are they?

The electron configuration of $Fe^{3+}$ is (atomic number of $Fe = 26$)

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

What does magnetic quantum number describe?

The quantum numbers of six electrons are given below. Arrange them in order of increasing energies. If any of these combination$(s)$ has/have the same energy,list them:
$(1).$ $n=4, l=2, m_l=-2, m_s=-1/2$
$(2).$ $n=3, l=2, m_l=1, m_s=+1/2$
$(3).$ $n=4, l=1, m_l=0, m_s=+1/2$
$(4).$ $n=3, l=2, m_l=-2, m_s=-1/2$
$(5).$ $n=3, l=1, m_l=-1, m_s=+1/2$
$(6).$ $n=4, l=1, m_l=0, m_s=+1/2$

Aqueous solution of which salt will not contain ions with the electronic configuration $1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6$?