Summary of Periodic Trends

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Ellis Song 4I
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Joined: Thu Jul 11, 2019 12:17 am

Summary of Periodic Trends

Postby Ellis Song 4I » Wed Oct 23, 2019 9:37 pm

- Atomic radii increase down a group and decrease across a period
- Ionic radii increase down a group and decrease across a period, cations are smaller than parent and anions are larger
- Ionization energy decreases down a group and increases across a period
- Electron affinity is high for elements at the top right of the periodic table, noble gases have negative electron affinity

Paige Lee 1A
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Joined: Sat Sep 07, 2019 12:16 am

Re: Summary of Periodic Trends

Postby Paige Lee 1A » Thu Oct 24, 2019 9:43 am

Could someone please explain why noble gases have a negative electron affinity?

TYun_1C
Posts: 52
Joined: Wed Sep 11, 2019 12:16 am

Re: Summary of Periodic Trends

Postby TYun_1C » Thu Oct 24, 2019 9:59 am

Since noble gases already have filled octets, they are extremely stable and do not want it gain another electron, which would make it much more unstable. Therefore, there is almost zero energy released (electron affinity) when an electron is added to a ground state noble gas,

Jasmine Fendi 1D
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Joined: Sat Aug 24, 2019 12:15 am

Re: Summary of Periodic Trends

Postby Jasmine Fendi 1D » Thu Oct 24, 2019 10:23 am

Can someone please explain why ionization energy increases as you move from left to right on the periodic table?

alicechien_4F
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Joined: Sat Jul 20, 2019 12:15 am

Re: Summary of Periodic Trends

Postby alicechien_4F » Thu Oct 24, 2019 1:03 pm

Since ionization energy is the energy required to remove an electron from a neutral atom, atoms of the left side of the period table would have the lowest ionization energy because alkali metals want to lose electrons to maintain a full valence shell and become a cation. The lower the ionization energy, the easier it will be for an atom to be cation. On the other hand, atoms on the right side of the periodic table rather gain electrons than lose them, so it'll take much more energy to remove the electrons than to gain them. Hope this helps!

Yailin Romo 4G
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Joined: Wed Feb 20, 2019 12:16 am

Re: Summary of Periodic Trends

Postby Yailin Romo 4G » Thu Oct 24, 2019 1:07 pm

Thank you for this helpful summary of periodic trends, what I would add to that table is which elements (metals, nonmetals) differ with their affinity and how their ionization energy differs as well.

Diana Chavez-Carrillo 2L
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Joined: Fri Sep 28, 2018 12:18 am

Re: Summary of Periodic Trends

Postby Diana Chavez-Carrillo 2L » Thu Oct 24, 2019 1:16 pm

Is electron affinity only important/ only affects Group 17 (according to Lavelle) and noble gases? Or why is it important to know the electron affinity?

Alan Wu
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Joined: Sat Sep 14, 2019 12:16 am

Re: Summary of Periodic Trends

Postby Alan Wu » Fri Oct 25, 2019 5:40 pm

Diana Chavez-Carrillo 3J wrote:Is electron affinity only important/ only affects Group 17 (according to Lavelle) and noble gases? Or why is it important to know the electron affinity?


It's important to know the electron affinity of elements probably because we can use that to measure how much energy is released or gained in reactions. Since electrons are lost and gained in reactions, the electron affinity and ionization energy can allow us to calculate the total energy of the reaction.


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