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### 3.33

Posted: Sun May 13, 2018 10:01 am
For these, how do we know which letter should be in the middle? I know it is lowest ionization energy but what if two elements are in two different rows and groups? How can you tell?

### Re: 3.33

Posted: Sun May 13, 2018 10:34 am
Hi,
Ionization energy increases across periods and decreases down columns. Keep this in mind when deciding which element has the lowest ionization energy (it will be closer to the lower left corner of the periodic table).

### Re: 3.33

Posted: Sun May 13, 2018 11:49 am
Also be mindful of exceptions, like oxygen, which has a lower ionization energy than nitrogen, yet is not in the center for the lewis dot of NO3.

### Re: 3.33

Posted: Sun May 13, 2018 2:50 pm
I think that another way you can determine which element has the lowest ionization energy between two elements that are in two different rows or groups is to use the concept of diagonal relationship which states that elements diagonal to each other (one period down and one group to the right) have very similar chemical properties, such as ionization energy. For example, you could thus say that carbon and phosphorus have a similar ionization energy, This would help you when trying to determine whether carbon or chlorine (part A problem 3.33) has the lowest ionization energy because since chlorine is more to the right than phosphorus, it will be carbon that has the lowest ionization energy between carbon and chlorine.

### Re: 3.33

Posted: Sun May 13, 2018 9:55 pm
Tarek Abushamma wrote:Also be mindful of exceptions, like oxygen, which has a lower ionization energy than nitrogen, yet is not in the center for the lewis dot of NO3.

Why does Oxygen have a lower ionization energy than Nitrogen? I am confused.

### Re: 3.33

Posted: Mon May 14, 2018 6:17 pm
Oxygen has a lower ionization energy than nitrogen because in the 2p orbital, oxygen has 4 electrons whereas nitrogen has 3. It is more stable for an element to have a half filled shell (as there are a total of 6 electrons that can occupy the 2p orbital), so therefore nitrogen would have a higher ionization than oxygen because it is in a more stable state.