Electron Affinity

[Emily_Bennett_3C]

What do they mean when they ask for the higher or lower electron affinity?

[Chem_Mod]

Electron affinity is the likelihood of an atom to gain an electron. The trend generally goes as follows: electron affinity increases from left to right across a period and decreases down a group on the periodic table.

[Christopher Reed 1H]

Hi!

Electron affinity is how much an atom wants to gain an electron. An atom will want to gain an electron if is super close to obtaining a half full orbital, a full orbital, or an octet in terms of valence electrons.

In terms of periodicity, electron affinity increase from left to right and bottom to top. The elements with the highest electron affinity (in decreasing order) are Cl > F > Br > I. Notice how Cl and F do not follow the trend I previously mentioned as chlorine is lower the fluorine yet it has a greater electron affinity. Also notice how these are all one electron away from being a noble gas! These guys really want that extra electron in order to obtain the stability of a noble gas.

Edit: I forgot to mention another exception to the trend which is carbon has a higher electron affinity than nitrogen. If you draw the aufbau diagram for both these elements you can see that carbon only needs on more electron to obtain a half full 2p orbital. It is important to remember that atoms want half or full orbitals so a useful strategy in comparing electron affinity might be to draw the aufbau diagram in cases where you are not sure.

[Alexandra_Cooper_4H]

Will we have to know the formula for electron affinity for the quiz tomorrow? Does anyone know?

[604744616]

How should we go about with memorizing or just remembering the trends in the periodic table? Any suggestions? And how can we also go about of remembering the exceptions in the periodic table?

[Joe Rich 1D]

Hey!

I like to remember trends by thinking of how a trend changes as you move up and to the right of the periodic table. Atomic radius and ionic radius are the biggest in the bottom left (at Cesium), and generally decrease as you move up and to the right. Ionization Energy, Electron Affinity, and Electronegativity are the biggest in the top right (Fluorine), and they decrease as you move down and left. Hope this trick helps!

[Ben Rolnik 1D]

just to add onto this -- since there were no homework problems which required performing electronegativity calculations, then you can be pretty sure questions like these won't show up on the tests.

In general, I would suggest focusing on the specific questions that arise from the homework problems. Otherwise you may be going above and beyond the course material (which we also never covered in lecture).

Hope that helps!

[Tara 1F]

Do you think in our exam next thursday the 24th that we will be asked questions that relate to the trends in the periodic table ? If so does anyone know a good way to remember them!

[derek1d]

I don't believe so. Apparently, the test next Tuesday will cover all new material since Exam 1 but not including topics from Exam 1 like the periodic trends.

[Nancy 1B]

I don't think there is a test on Tuesday... unless I'm mistaken?

[smuhammad1Section1E]

So from my understanding, there is a way to calculate the electron affinity...if that is the case, how would I go about doing such calculations.

[Tara 1F]

The test is next thursday the 24th :)

[Tara 1F]

Oops I mean thursday the 27th.