How many unpaired electrons are present in a carbon atom in its ground state?

Which of the following rules or principles states that "No two electrons in an atom can have the same set of four quantum numbers"?

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 $3f$

Identify the nodal planes for the $p_x$,$p_y$,and $p_z$ orbitals.

When the principal quantum number is $n = 3$,the possible values of the azimuthal quantum number $(l)$ are:

Which of the following set of quantum numbers represents the highest energy of an atom?