I understand all other periodic trends ( atomic radius, ionization energy) expect this one!
In: Chemistry
Electron affinity, as the name suggests, is how much an atom “wants” to add another electron. It’s generally a negative number because energy is released (i.e. the atom is more stable) when an electron gets added.
In general, atoms want to have full shells and subshells. In other words, they want to have the same number of electrons as the noble gases all the way on the right side of the periodic table. Elements close to the right side like fluorine and chlorine are just 1 atom short of this number of electrons so adding an electron is really good for their stability. Consequently, adding an electron allows them to release a lot of energy. Elements further to the left are multiple electrons short of a full shell, so it’s less of a big deal if they get another electron. This means that less stability is added and less energy gets released.
Some elements have positive values for electron affinity, meaning that it takes energy to add an electron. In other words, the atoms don’t “want” another electron. This is most evident for the noble gases since they’re starting out in the desirable position of having full shells.
Basically how much the element “wants/attracts” (aka affinity) the electrons (to go) towards the nucleus. All the periodic trends relate to one another and build off of one another.
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