The number of radial nodes in $3s$ and $2p$-orbitals, respectively are

Statement $A$: An orbital can accommodate a maximum of two electrons.
Reason $R$: Two electrons in an orbital produce opposite magnetic fields.

The number of unpaired electrons in cobalt atom is (atomic number of $Co = 27$)

Which of the following orbitals are degenerate? $3d_{xy}, 4d_{xy}, 3d_{z^2}, 3d_{yz}, 4d_{yz}, 4d_{z^2}$

Which orbital among the following has zero radial nodes and $2$ angular nodes?

The electrons identified by quantum numbers $n$ and $l$ :
$A. n=4, l=1$ $B. n=4, l=0$
$C. n=3, l=2$ $D. n=3, l=1$
can be placed in order of increasing energy as :