Trends of ionic radius

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manasa933
Posts: 72
Joined: Fri Sep 29, 2017 7:04 am

Trends of ionic radius

Postby manasa933 » Mon Oct 23, 2017 11:06 pm

Why is the following true:
Cations are smaller than their parent atoms, whereas anions are larger.

Nicole Jacobs 1C
Posts: 59
Joined: Thu Jul 13, 2017 3:00 am

Re: Trends of ionic radius

Postby Nicole Jacobs 1C » Mon Oct 23, 2017 11:08 pm

Electrons make the atom bigger because they increase the number of shells the atom has. So losing electrons (becoming cation) would mean you are reducing the number of energy levels and therefore decreasing the size of the atom. Vice versa, since an anion is gaining electrons, it has more shells than the neutral atom, meaning it is bigger than the original element.

Hannah Chew 2A
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Re: Trends of ionic radius

Postby Hannah Chew 2A » Tue Oct 24, 2017 10:06 am

Well the previous reply is not always true because sometimes the ions doesn’t lose or gain enough electrons to subtract or add an energy level. Sometimes you can remove one electron and it would still have the same principal quantum number. Cations are smaller because cations have less electrons than their parent atoms. Less electrons mean less electron-electron repulsions, so the ionic radius is smaller. Conversely, anions are larger because they have more electrons, and therefore, more electron-electron repulsions, than the parent atom.

Kendall Schemmer 1I
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Joined: Fri Sep 29, 2017 7:03 am

Re: Trends of ionic radius

Postby Kendall Schemmer 1I » Thu Oct 26, 2017 5:24 pm

Hannah is correct, the atom doesn't necessarily lose or gain an entire shell when it loses or gains electrons. When e- are lost, the atom is a cation and has more protons than e-. Therefore, the positive charge of the protons can pull more on each e- than it could in the atom's neutral state. The e- will get pulled closer to the nucleus and the atom is smaller. When e- are gained, there are more e- than protons, so the protons have less "pull" on the e-. The e- can spread out easier and the e- cloud increases in size away from the nucleus.

StephanieRusnak
Posts: 19
Joined: Fri Sep 29, 2017 7:07 am

Re: Trends of ionic radius

Postby StephanieRusnak » Thu Oct 26, 2017 8:42 pm

cations are positive, meaning they lost electrons and are smaller, whereas anions gain electrons and are larger


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