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### Help on 1F.3

Posted: Sun Oct 20, 2019 9:57 pm
For this question I was wondering how the charges on the elements of this question affect ionic radium. Will the extra electrons influence the radium at all?

Place the following ions in order of increasing ionic radius: S^2-, Cl^-, P^3-

### Re: Help on 1F.3

Posted: Sun Oct 20, 2019 10:05 pm
It influences it a lot. More electrons means higher orbitals have to filled to fit all the electrons in, and therefore the radius of the atom should increase.

In this problem, each atom has the same amount of electrons, but some have fewer protons, and therefore, pull the electrons in less, and have lower radius as a result.

### Re: Help on 1F.3

Posted: Sun Oct 20, 2019 10:10 pm
Yes, extra electrons do affect radius of an atom because compulsion forces among electrons push them away from each other. However, this information is not relevant to this question. In this case, S^2-, Cl^1-, P^3- all have the same electron configuration of [Ar], meaning that they have the same number of electrons. Since Cl has more protons in the nucleus than S does, it exerts more attraction force to electrons and thus has a smaller radius. Same reason with S and P, P with a smaller number of protons will exert less attraction forces and thus has a larger radius. Therefore, the answer to this question is Cl,S,P, in an increasing order.

### Re: Help on 1F.3

Posted: Mon Oct 21, 2019 4:28 pm
Mulin_Li wrote:Yes, extra electrons do affect radius of an atom because compulsion forces among electrons push them away from each other. However, this information is not relevant to this question. In this case, S^2-, Cl^1-, P^3- all have the same electron configuration of [Ar], meaning that they have the same number of electrons. Since Cl has more protons in the nucleus than S does, it exerts more attraction force to electrons and thus has a smaller radius. Same reason with S and P, P with a smaller number of protons will exert less attraction forces and thus has a larger radius. Therefore, the answer to this question is Cl,S,P, in an increasing order.

Like Mulin_Li said, the three ions have the same electron configuration meaning they are isoelectronic atoms with the same number of electrons. Just because they have the same number of electrons does not mean they have the same chemical properties, due to the varying nuclear charges.