Central atom

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Hyein Cha 2I
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Central atom

Postby Hyein Cha 2I » Tue Nov 07, 2017 11:08 am

Hi, I found on google that the least electronegative atom should be the central atom, but we learned in class that it should be the atom with least Ionization energy. Which is the correct one?

Also, in one of the book examples in chapter 3, it asked to draw the lewis structure for KSCN ion, so SCN- . However, it then said that Carbon has the lowest ionization energy from the three elements... but I thought Sulfur has the lowest Ionization energy. Can someone please explain?

Meredith Steinberg 2E
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Re: Central atom

Postby Meredith Steinberg 2E » Tue Nov 07, 2017 11:28 am

If you think about trends on the periodic table, ionization energy decreases to the left, as does electronegativity (so you can think about it both ways). For SCN-, the overall trend for ionization energy is that it decreases down and to the left of the periodic table (carbon is further left, and therefore has a lower ionization energy).

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Re: Central atom

Postby AtreyiMitra2L » Tue Nov 07, 2017 12:05 pm

They are both right. If it has low ionization energy, it has low electron affinity. Atoms with a low ionization energies are one the left of the periodic table. They have a low ionization energy bc they really want to give up that electron. Atoms with a low electron affinity are also on the left of the periodic table as they don't particularly want that extra electron. In terms of C, C is an excpetion to the rule. It will always go in the center regardless.

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