Electron affinity

[Matia Kim 1B]

The textbook says that electron affinity increases towards the right of the periodic table. Why is that? Also is there a pattern or affinity going down the groups of the periodic table?

[MadelynNguyen1F]

Electron affinity going from left to right of the periodic table increases because the amount of protons an element has also increases. There is an attractive charge between the positively charged protons in the nucleus and the negatively charged electrons. So, the outer electrons are more attracted to the protons in the nucleus as the number of protons increases.

[MadelynNguyen1F]

I believe that atoms with a full octet are an exception though.

[Sarah Brecher 1I]

I believe that a full octet is the exception because once the shell is filled, the atom is stable and therefore there is no need for an electron to be added to the shell.

For example, if you were asked which has a higher electron affinity between elements Ne and Cl, Cl would have the higher electron affinity since it wants to complete its shell whereas Neon's shell is already filled.

[Ashley Martinez 1G]

In general, electron affinities become less negative from top to bottom of a group (there's a few exceptions due to the difficulty of accurately measuring electron affinity).