Figure 1. A ‘snap shot’ of the lithium atom. The spherical color gradient represents the central field, U(rk). The structure of the central field may vary with the atomic number

From

Modeling of Ionization Energy of Elements Using Hartree-Fock Method: An Introduction to Computational Quantum Chemistry for Undergraduate Students

Krishnamohan G P, Thomas Mathew, Simi Saju, James T. Joseph

World Journal of Chemical Education. 2017, 5(3), 112-119 doi:10.12691/wjce-5-3-6