The number of electrons in the outermost shell of an element with atomic number $15$ is . . . . . . .

The number of orbitals in the fourth principal quantum number $(n = 4)$ is:

How many electrons are present in an atom with atomic number $Z = 104$ for which $(n + l) = 8$?

Identify the incorrect statement from the following.

Which of the following sets of quantum numbers represents the orbital with the highest energy?

The electronic configurations of four elements are given in brackets: $L\,(1s^2, 2s^2 2p^1)$; $M\,(1s^2, 2s^2 2p^5)$; $Q\,(1s^2, 2s^2 2p^6, 3s^1)$; $R\,(1s^2, 2s^2 2p^2)$. Which element would most readily form a diatomic molecule?