A lithium atom has three electrons. Two inner electrons form a spherical cloud and the third electron moves outside this cloud in a Bohr orbit; n=1 is not available to it. Using this model, find the ionization energy of lithium in its ground state.
Physics · Atomic Structure and X-rays
JEE Mains Advanced

Question

A lithium atom has three electrons. Two inner electrons form a spherical cloud and the third electron moves outside this cloud in a Bohr orbit; n=1 is not available to it. Using this model, find the ionization energy of lithium in its ground state.

Physics · Atomic Structure and X-rays

G1 Physics · Accepted Answer

The outer electron sees an effective nuclear charge close to +e, but the n=1 orbit is unavailable, so the ground configuration for that electron is n=2. Using |E₂|=13.6/4 eV gives an ionization energy 3.4 eV.