smaller cations

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Lauren Bui 1E
Posts: 54
Joined: Sat Jul 20, 2019 12:15 am

smaller cations

Postby Lauren Bui 1E » Wed Nov 06, 2019 12:24 pm

How can you tell what the smallest cation is? Is it based on charge or size/atomic radii or something else?

Emily Chirila 2E
Posts: 112
Joined: Sat Jul 20, 2019 12:16 am

Re: smaller cations

Postby Emily Chirila 2E » Wed Nov 06, 2019 12:31 pm

Cation size decreases up and decreases to the right. They get smaller as you go up because number of orbitals decrease, and get smaller as you go right as you add more positive charge (holds in electrons tighter). Same trend as atomic radius. The smaller the cation leads to more polarizing power.

Robert Tran 1B
Posts: 118
Joined: Thu Jul 11, 2019 12:15 am

Re: smaller cations

Postby Robert Tran 1B » Wed Nov 06, 2019 12:48 pm

I'm assuming if you're asked to find the smallest cation, it is given that all the cations have the same amount of valence electrons. In this case, the smallest cation would have the highest amount of protons because this would mean the nucleus has a stronger pull on the electrons.

Cynthia Gong 1L
Posts: 51
Joined: Fri Aug 09, 2019 12:15 am

Re: smaller cations

Postby Cynthia Gong 1L » Wed Nov 06, 2019 10:58 pm

Cation radii follows the normal atomic radii trend. It increases across a period and decreases down a group. This is because moving across, the number of protons increases, thus increasing effective nuclear charge and decreases the size. If we have 3 cations that are isoelectronic, for instance: Na+, Mg2+, and Al3+, the smallest cation would be the one with the greatest number of protons, since it has the strongest effective nuclear charge and is able to pull in the remaining electrons closer. In this case, Al3+ would be the smallest.

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