Mg+(g) + e- → Mg(g) + energy

Explanation:

* Mg+(g) represents a gaseous magnesium cation.

* e- represents an electron.

* Mg(g) represents a gaseous magnesium atom.

* energy represents the energy released or absorbed during the process.

Electron affinity is the change in energy when an electron is added to a gaseous atom or ion.

In the case of Mg+, adding an electron results in the formation of a neutral Mg atom. This process is exothermic, meaning energy is released, and the electron affinity value is negative.

Note: It's important to remember that the electron affinity of a cation is usually much less negative than the electron affinity of a neutral atom. This is because the cation already has a positive charge, making it less attractive to an additional electron.