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3.33 and ionization energy

Posted: Sun May 20, 2018 2:57 pm
by Zuri Smith 1A
I thought that:
a) ionization energy increases across a period and up a group, and
b) The element with the highest ionization energy is chosen as the central atom when creating a lewis structure.

Question 3.33 part b asks us to write the lewis structure of COCl2. I thought that O or even Cl had higher ionization energies than C, but the correct lewis structure depicts C as being the central atom. Why is that?

Part C left me similarly puzzled, with N being chosen as the central atom when F has a higher ionization energy than both N and O. Why is this the case?

Re: 3.33 and ionization energy

Posted: Sun May 20, 2018 4:06 pm
by Mario Reyes 1C
We actually choose the atom with the lowest ionization energy for the central atom. Even with that, part c) is still confusing since O has a lower ionization energy than N does. Anybody understand why?

Re: 3.33 and ionization energy

Posted: Mon May 21, 2018 9:35 pm
by Zuri Smith 1A
According to pg. 78 in the textbook, "In simple chemical formulas, the central atom is often written first, follow by the atoms attached to it." Perhaps this is the reason why the correct answer is what it was.

Re: 3.33 and ionization energy

Posted: Mon May 21, 2018 10:22 pm
by Bianca Nguyen 1B
O may have a lower ionization energy than N, but it has a higher electronegativity than N, thus making N the central atom as it is the least electronegative. In the beginning of Chapter 3, the book said that we would say the atom with the “lowest ionization energy” is the center atom, but later on in the chapter, it says to use “lowest electronegativity” instead. The trends for both are almost the same but with slight differences, as seen in this problem.