The total number of electrons in all orbitals having principal quantum number $n = 2$ and azimuthal quantum number $l = 1$ is ..........

Two electrons occupying the same orbital are distinguished by

Consider the electronic configuration for neutral atoms:
$(i) \ 1s^22s^22p^63s^1$ $(ii) \ 1s^22s^22p^64s^1$
Which of the following statements is/are false?
$(a)$ Energy is required to change $(i)$ to $(ii)$
$(b)$ $(i)$ represents $Na$ atom
$(c)$ $(i)$ and $(ii)$ represent different elements
$(d)$ More energy is required to remove one electron from $(i)$ than $(ii)$

Which of the following sets of quantum numbers $(n, l, m, s)$ is incorrect?

Which of the following ions does not have the electronic configuration of neon $(Ne)$?

The set of principal $(n)$,azimuthal $(l)$ and magnetic $(m_l)$ quantum numbers that is not allowed for the electron in $H$-atom is