Question

What is the name for the energy required for an electron to be added to a neutral atom in its gaseous form?

Answer 1

electron affinity

Electron affinity is the energy required for an electron to be added to a neutral atom in its gaseous form. Because most atoms release energy when an electron is added, most electron affinity values are negative. These values generally become more negative  more energy is released  as you move left to right across the table or from bottom to top.