Which element would release the most energy while adding an electron to a neutral atom in the gas phase?
a. na
b. al
c. br
d. s

The correct option is: C. Br      

Explanation:

Electron affinity refers to the energy lost by a gaseous atom when it accepts an electron in its valence shell. When the gaseous atom gains an electron it forms a negatively charged ion called anion.

Chemical elements that have a more stable anion than neutral atoms tend to have greater electron affinity.

Halogens have high electron affinity as they readily accept an electron to achieve the stable noble gas electron configuration.

Therefore, the halogen, bromine (Br) has the highest electron affinity as it would release the most energy when accepting an electron.

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.