The electron affinity of an element is positive if energy is absorbed during the process of accepting an electron and negative if energy is released during the process. Using the electron configuration of the atom or ion undergoing the addition of an electron, predict whether the electron affinity will be positive or negative for the following reactions, and classify them accordingly. Na(g)+ 1e^- → Na^-(g)
Mg(g)+1e^- → Mg^-(g)
Br(g)+ 1e^- → Br^-(g)

See explanation

Explanation:

Electron affinity is the energy released when an extra electron is added to a neutral gaseous atom. A negative value of electron affinity indicates that energy is given out and vice versa.

Metals have positive electron affinity since electrons rarely accept electrons, so;

Na(g)+ 1e^- → Na^-(g)      positive

Mg(g)+1e^- → Mg^-(g)      positive

For the last case; Br(g)+ 1e^- → Br^-(g), the electron affinity for the non-metals is negative. hence the answer

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.