Ionization energy vs. electron affinity [ENDORSED]

[Annah Khan 1B]

Hello! I'm still not sure what the difference is between ionization energy and electron affinity. Can someone please explain these concepts to me further? Thank you in advance!

[Natalie Espadas 1A]

I believe that ionization energy is the energy required to remove an electron. Electron affinity is how likely it is to attract an electron. I believe these are the main differences, but if anybody would like to correct me, please do! thank you in advance!

[Sohini Halder 1G]

Ionization energy and electron affinity are definitely related!

Ionization energy is the energy to remove an electron, or ionize it, from an atom. Ionization energy increases left to right across a period, which makes sense because as the valence shell fills in the atom moving left to right, the elements farther to the right will "want" an electron more than those on the left to fill their valence shell and become stable. The ionization energy for Lithium is much lower than Fluorine for that reason. Lithium would more likely lose an electron to have valence shell like a noble gas than Fluorine.

Electron affinity is how much the atom "wants" an electron. F "wants" an electron more than L "wants" one, for the same reasons described above. Electron affinity increases left to right across a period and increases going up the PT.

You can think of it this way: If an atom has a high ionization energy, it has a high electron affinity as well because electrons don't "want" to leave and therefore it takes more energy to ionize the atom.

[Rachel Formaker 1E]

Another way to think about this is that a low ionization energy corresponds to likelihood to form a cation (because it is easier to remove the electron) and a high electron affinity corresponds to likelihood to form an anion (because more energy is released when an electron is added).

This is helpful in remembering which elements tend to have which levels of ionization energies and electron affinities because Group 1 & 2 elements usually form cations (and therefore have low ionization energies) and Group 17 & 18 elements usually form anions (and therefore have high electron affinities).

[Karen Ung 2H]

According to the book, the ionization energy is the minimum amount of energy needed to remove an electron from a gas-phase atom, and electron affinity is the energy released when an electron is added to a gas-phase atom.

[Girija_3E]

According to the book, the ionization energy is the minimum amount of energy needed to remove an electron from a gas-phase atom, and electron affinity is the energy released when an electron is added to a gas-phase atom.

by "gas-phase," does this just mean a noble gas? thank you!!