Hydrogenic means *like hydrogen*.
Hydrogenic species are those that, like hydrogen, consist of a single nucleus orbited by a single electron.

^{+}. Image by Yzmo.

Examples of hydrogenic ions are: He^{+}, Li^{2+}, Be^{3+}, B^{4+}, C^{5+}, etc.

Mathematically, hydrogenic species are two-body systems, which are much more easily analyzed than systems involving more than two bodies.

Exact, analytic solutions of the Schrödinger equation are possible only for two-body systems; for all other atoms, ions, and molecules, no analytic solutions exist; approximation methods are utilized to solve the Schrödinger equation.

The Schrödinger equation can be used to find the wave function Ψ and its square Ψ^{2} for atoms, ions and molecules: analytic solutions for hydrogenic species; approximations for all others.

From Ψ and Ψ^{2} we get electrons' quantum numbers and the familiar shapes of atomic orbitals.

For example, the image shows the 1s orbital of He^{+}.
The probability density of the electron is indicated by the darkness of shading.