What is the reaction that corresponds to the first ionization energy of rubidium, rb?

Ionization is a process in which an electron present in the outermost orbital of an atom gets knocked out by absorbing an appropriate amount of energy. Release of electron from a neutral atom results in the formation of a cation- a positively charged ion.

Rubidium (Rb) is an alkali metal with a valence electron configuration of 5s¹. Ionization results in the loss of this '5s' electron forming a Rb+ ion. The reaction can be expressed as:

Rb (5s¹) → Rb⁺ (5s⁰) + e⁻