The atomic number of an element having the valence shell electronic configuration $4s^2 4p^6$ is

In the following pairs,which orbital experiences greater nuclear attraction?
$(i)$ $4f$ and $5d$ $(ii)$ $4d$ and $5s$ $(iii)$ $7s$ and $5f$ $(iv)$ $7p$ and $5p$
$(v)$ $3d$ and $3f$

Which of the following orbitals has/have zero probability of finding the electron in the $xy$ plane?

The orientation of an atomic orbital is governed by

Explain the significance of the $+ve$ and $-ve$ signs in the context of atomic orbitals.

Explain how the energy of an orbital and the extent of shielding in the same shell depend on the shape of the orbitals.