In the ground state of a neutral atom, the highest energy electron resides in an orbital that has 2 radial nodes and 1 angular node. If the atom possesses exactly 3 unpaired electrons, its atomic number is:

Step-by-step solution

The number of angular nodes is equal to the azimuthal quantum number l . Thus, l = 1 , which corresponds to a p -orbital. The number of radial nodes is given by the formula n - l - 1 . Given that the number of radial nodes is 2 and l = 1 : n - 1 - 1 = 2 n = 4 The highest energy electron is therefore in the 4 p subshell. For a p -subshell to have exactly 3 unpaired electrons, it must be exactly half-filled according to Hund's rule of maximum multiplicity. This gives the configuration 4 p ³ . The complete ground stat