Question

What factor in the quantum mechanical equations of many-electron atoms makes them analytically unsolvable?

A. The spin operation

B. The need for the Born-Oppenheimer approximation

C. The non-zero communicator between the electron position and momentum

D. The electron-electron repulsion term

Answer 1

C. The non-zero communicator between the electron position and momentum

This is because the procedure to obtain analytical solution for a two-particle ( or more particle) problem relies on the center-of-mass separation trick which works.

if the potential energy depends only on the relative positions of the particles