An element has the electronic configuration $1s^2, 2s^2 2p^6, 3s^2 3p^2$. Its valence electrons are

What would be the electronic configuration of $Cs (Z=55)$ in each case?
$(a)$ If there were three possibilities of the electron spin.
$(b)$ If the quantum number,$l$,could have the value $n$,and if all the rules governing electron configuration were otherwise valid.

In a chromium atom,the number of electrons which have $n = 2$ and $l = 1$ is:

What do the quantum numbers $n$,$l$,and $m_l$ represent?

The shape of $s$-orbital is

The number of orbitals present in the shell with $n = 4$ is