Final answer:
Complete the electron configuration for each parent atom by starting with the neutral species, then adjust for ion charges by adding or removing electrons to achieve the ionic electron configuration. Use noble gas abbreviations for core electrons and then list the valence electron configuration.
Step-by-step explanation:
To complete the ground state electron configuration for ions, we need to start by writing the electron configuration for each of the parent atoms. If the atom is neutral, we can then add or remove electrons to achieve the electron configuration of the ion, keeping in mind the charge of the ion directly corresponds to the number of electrons added (negative charge) or removed (positive charge).
For example, for zinc (Zn), which has an atomic number of 30, the neutral atom's electron configuration would be [Ar]3d¹⁰₄s². If Zn forms a +2 cation (common for Zn in many compounds), two electrons are removed, which usually come from the highest energy sublevel, after which Zn²⁺ will have the electron configuration of [Ar]3d¹⁰.
In the case of chromium (Cr), the neutral atom's electron configuration is [Ar]3d⁵₄s¹. If we are to turn this into a common chromium ion, such as Cr³⁺, we would remove three electrons, resulting in the electron configuration [Ar]3d³.
To abbreviate the electron configuration for an ion, we use the nearest noble gas to represent the core electrons, followed by the electron configuration of the valence electrons. For instance, the phosphorus (P) atom would be [Ne]3s²₃p³ as its abbreviated electron configuration.