Electron affinity versus ionization energy [ENDORSED]

[William Cryer 1L]

Are electron affinity and ionization energy the same thing? Or rather, do they have the same trend on the periodic table? How much an atom is attracted to electrons seems to me very closely related to its ionization energy. Could anyone clarify these two for me? Thanks.

[Kevin Liu 3G]

They are not technically the same thing but they have the same trends. Electron affinity is essentially how likely it is an element is to form an ion whereas ionization energy is the energy needed for said element to form an ion. So one is the likeliness of an element being an ion while the other is the energy needed to form the ion.

[Curtis Wong 2D]

Electron Affinity is the energy that is released when an electron is added to a gas phase atom, while ionization energy is the energy needed to remove an electron from an atom. The further away an electron is from a nucleus, the easier it becomes to remove the electron.

Thus, for ionization energy,
it decreases down a group, and
increases across a period.

However, for electron affinity, it is a little bit less clear. There's no definite pattern for it, but generally, there's a higher electron affinity for elements in the top right of the periodic table (not including the noble gases so up to group 17). Adding an electron to a filled valence shell ie, group 12 or the noble gases group, is unfavorable and will require energy to keep that electron there. Basically, you need to take a look at the electron configuration to get a general idea of how it's gonna change.

[Rachel Lu_dis1H]

Electron affinity and ionization are different. Ionization energy is the energy NEEDED to remove an electron from an atom in the gas state while electron affinity is the energy RELEASED when an election is added to a gas-phase atom. Ionization energy increases up and to the right because the smaller an atom is, the more energy it takes to remove an electron from the atom (there's more pull on electrons the closer they are to the nucleus). Electron affinity increases to the right where fluorine has the highest electron affinity. The trend is more complicated because it depends on how many electrons there are in an orbital and where they're placed.