The number of nodal planes (planes of zero electron density) in the $d_{xy}$ orbital is:

Consider the following pairs of electrons:
$(A)$ $(a)$ $n=3, l=1, m_{l}=1, m_{s}=+\frac{1}{2}$
$(b)$ $n=3, l=2, m_{l}=1, m_{s}=+\frac{1}{2}$
$(B)$ $(a)$ $n=3, l=2, m_{l}=-2, m_{s}=-\frac{1}{2}$
$(b)$ $n=3, l=2, m_{l}=-1, m_{s}=-\frac{1}{2}$
$(C)$ $(a)$ $n=4, l=2, m_{l}=2, m_{s}=+\frac{1}{2}$
$(b)$ $n=3, l=2, m_{l}=2, m_{s}=+\frac{1}{2}$
The pair$(s)$ of electrons present in degenerate orbitals is/are...... .

Identify the pair of elements in which the ratio of the number of $s$-electrons to $p$-electrons is $2:3$.

The electronic configuration of calcium ion $(Ca^{2+})$ is

Which of the following is correct for $2p$-orbitals?

Which of the following is not correct for the electron distribution in the ground state for $4s$ and $3d$ orbitals?