Difference between anions and cations?

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Alexander Hari 1L
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Joined: Wed Feb 14, 2018 3:02 am

Difference between anions and cations?

Postby Alexander Hari 1L » Thu May 10, 2018 2:48 pm

I'm still having trouble between how these two work. From my understanding, an anion is an element such as C- that is a Carbon atom that lost an electron, so if it has one less electron shouldn't it be more similar to Boron which is one element to the left and not like Nitrogen which would have one more electron?
Another example in the textbook (3.5.a) asks for the ground configuration of a Cu+ ion but shows the answer as [Ar]3d10 which is like Nickel (one element to the left and also one electron less than a normal Cu). Can anyone clarify?

Beverly Shih 1K
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Re: Difference between anions and cations?

Postby Beverly Shih 1K » Thu May 10, 2018 2:57 pm

I think you may have gotten mixed up about anions vs. cations. You're right that anions have a negative charge, but that's because they have gained an extra electron--remember that electrons have a negative charge so having extra electrons would make the atom more negative. Cations therefore have a positive charge because they have lost one or more electrons, so they are "less negative," meaning more positive than neutral atoms. One way to remember this is to think of cations as cats--they have paws and so cations are pawsitive!
In your example, C- has a negative charge so it has an extra electron. It thus has the same number of electrons as the element to the right, nitrogen.
In the example from the book, first determine the electron configuration of Cu which is [Ar] 3d10 4s1 (not [Ar] 3d9 4s2 because the d-subshell wants to be full--I think there are several threads about this already). Then, because you're looking for the electron configuration for Cu+, the cation, you remove the outermost electron to get that positive charge. This leaves you with [Ar] 3d10.
In summary, anions have a negative charge, gain electrons, and are isoelectronic to elements to the right of them in the periodic table. Cations have a positive charge, lose electrons, and are isoelectronic to elements to the left of them in the periodic table.

NabilaNizam-1K
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Re: Difference between anions and cations?

Postby NabilaNizam-1K » Thu May 10, 2018 8:15 pm

Anions: when an atom gains electrons and form a negatively charged ion due to the increased number of electron
Cations: when an atom loses electrons and form a positively charged ion due to the decreased number of electron

This is basically how I remember it so I hope it helps!

Samantha Castro 1D
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Joined: Wed Nov 15, 2017 3:03 am

Re: Difference between anions and cations?

Postby Samantha Castro 1D » Fri May 11, 2018 9:41 pm

Cations give up electrons in order to reach octet. Anions form ions that are larger than their original atoms. Also, anions are negatively charged ions, while cations are positively charged ions.


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