Two electrons $A$ and $B$ in an atom have the following set of quantum numbers:
$A: n=3, l=2, m_l=-2, m_s=+1/2$
$B: n=3, l=0, m_l=0, m_s=+1/2$
What is true for $A$ and $B$?

Identify the correct statements:
a) In an atom,the maximum number of electrons with $n=4$ and $m_s=+\frac{1}{2}$ is $16$.
b) There are $4$ subshells associated with $n=5$.
c) $n=2, l=1, m_l=0$ and $m_s=-\frac{1}{2}$ is a possible set of quantum numbers.
d) The number of radial nodes for $3s$ orbital is $2$.

The quantum number which explains the line spectra observed as doublets in the case of hydrogen and alkali metals, and doublets and triplets in the case of alkaline earth metals is:

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 :

Which of the following configurations is correct for iron $(Fe)$?

The number of unpaired electrons in an atom with atomic number $29$ is .....