## Identifying an element from a given Lewis Structure (3.37)

Mike Matthews 1D
Posts: 59
Joined: Fri Sep 29, 2017 7:04 am

### Identifying an element from a given Lewis Structure (3.37)

Hi. I was hoping someone could explain to me how to do homework problem 3.37. The problem says, "The following Lewis structure was drawn for a Period 3 element. Identify the element." The Lewis Structure shows a central atom "E" surrounded by 3 Cl atoms and 1 O atom. There is a double bond between the central atom and the O atom and single bonds between the central atom and the three Cl atoms. I'm confused because all the atoms in period 3 could have the expanded octet shown in this Lewis structure which means that in order to identify the element one must take formal charge into account. However, I'm not quite sure how to start this problem. Any help would be greatly appreciated.

Diane Bui 2J
Posts: 61
Joined: Sat Jul 22, 2017 3:00 am

### Re: Identifying an element from a given Lewis Structure (3.37)

I'm hoping this is right, but from what I would do is to count up the total number of electrons in the molecule, which seems to me that there are 32 electrons. 21 electrons are from Chlorine due to its 7 valence electrons, and there are 3 Chlorines in the molecule. 32-21 leaves 11 electrons left over. 6 electrons come from Oxygen because Oxygen has 6 valence electrons. That leaves 11-6=5 electrons that should come from E, meaning that it should come from the Group 15 elements. Since the problem states that it is from the 3rd period, the element E should be Phosphorus.
Hope this helps!!

Camille 4I
Posts: 57
Joined: Sat Aug 24, 2019 12:18 am

### Re: Identifying an element from a given Lewis Structure (3.37)

Hi, are you using the formal charge equation to figure out that this is phosphorus?