1. Periodic Trends Electron Affinity

2. ► The energy change that occurs when an atom gains an electron ► How much an atom “likes” to gain electrons

3. I love electrons!!

4. ► Atoms with a high attraction for electrons will have more negative values for their Electron Affinity Compare K and F based on Electron Affinity: ► F’s value for EA will be more negative than K’s because we know that F wants to gain an electron whereas K wants to lose an electron.

5. Electron Affinities (Main Group Elements) H-73 Li-60 Na-53 K-48 Rb-47 Be19Mg19 Ca-2 Sr-5 B-27C-122N7O-141F-328 Ne 29 Al -43 Si-134P-72S-200 Cl -349 Ar35 Ca-30Ge-119As-78Se-195Br-325Kr39 In-30Sn-107Sb-103Te-190I-295Xe41 He 21 Generally increasing Electron Affinity

6. Things to Note: ► The Noble Gases have positive EA meaning they DO NOT WANT TO GAIN AN ELECTRON ► The Halogens (Group 7A) have the largest (most negative) EA because they only need one electron to have the electron configuration of a noble gas ► Both of the above are due to the Octet Rule

7. Octet Rule Atoms tend to gain, lose, or share electrons in order to have a set of 8 electrons in their valence (outermost) energy level (except for elements in the first energy level, they want 2 in their valence energy level)

8. How to rank Electron Affinities: ► Noble gases will always have the lowest electron affinities (positive values) ► Nonmetals will have the higher electron affinities (more negative values) than metals ► When comparing two nonmetals, the one that is closest to becoming a noble gas will have the higher Electron Affinity  If in the same group, the smaller one will have the higher electron affinity

9. Na or Cl? Which has the higher EA (more negative value) ► Cl ► Because Cl is a nonmetal and it only needs one more electron whereas Na needs to lose an electron so gaining one would not be helpful!

10. Ne or Br? Which one will have the smaller EA (least negative value) ► Ne ► Ne is a noble gas so it will always have the smallest Electron Affinity

11. O or F? Which has the largest EA? ► Remember, largest EA = more negative value ► Answer: F ► Because both are nonmetals but fluorine is closer to becoming a noble gas (only has to gain one)

12. I or Cl? Which has a higher EA? ► Cl ► They are both nonmetals and are in the same group but Cl is smaller so it has a better ability to attract electrons to its nucleus since it is closer to the valence level