1. Electron Affinity Trend Visit this website first!! http://chemguide.co.uk/atoms/prop erties/eas.html

2. Electron Affinity The energy change associated with adding an electron to a gaseous atom. Easiest to add to group 17. Gets them to full energy level. Increase from left to right atoms become smaller, with greater nuclear charge. Decrease as we go down a group.

3. Electron affinity (EA) of an element E is defined as the energy change that occurs when an electron is added to a gaseous atom: E (g) + e --  E — (g) energy change = EA. Electron affinities can be negative (in which case energy is released when an electron is added) or positive (in which case energy must be added to the system to produce an anion) or zero (the process is energetically neutral). Halogens have the most negative electron affinities. Electron affinities become more negative as we go across a row of the periodic table. Pattern corresponds to the increased effective nuclear charge felt by the valence electrons across a row, which leads to increased electrostatic attractions between the added electron and the nucleus (a more negative EA).