How Do I Complete This Lewis Structure?

[JeweliaHeart]

Homework Statement

Draw the best Lewis Dot Structures the following species:
ClF4+

Homework Equations

none

The Attempt at a Solution

I calculated that there should be a total of 34 e- in the Lewis structure":
7 (1 chlorine atom) + 28 ( 7 from each of the four fluorine atoms) - 1(b/c the atom has a plus one charge)= 34 e-

My Lewis structure (what I have in it so far) is in the attachment below. I don't know how to add in the two other electrons w/o violating the octet rule or even where they should go if I did add them.

 

[DrClaude]

The lone pair sits on the chlorine atom. You have to invoke higher-energy orbitals, so the octet rule is not followed.

 

[JeweliaHeart]

Well, thank you.

And this must be possible b/c the chlorine atom is the third period so it can utilize d orbitals, right?

If so, that makes perfect sense to me, but just for future reference is there some hard & fast rule to apply whenever one comes across problems like these: For example, the extra electrons always goes to the atom that can support d orbitals (i.e. period 3 or higher elements)?

 

[DrClaude]

And this must be possible b/c the chlorine atom is the third period so it can utilize d orbitals, right?

Right. I should've specified that when I said "higher-energy orbitals", it will only be stable if the difference in energy is not to big, and therefore the orbitals must come from the same shell.

If so, that makes perfect sense to me, but just for future reference is there some hard & fast rule to apply whenever one comes across problems like these: For example, the extra electrons always goes to the atom that can support d orbitals (i.e. period 3 or higher elements)?

I wouldn't say that there are "hard & fast rules", especially since Lewis diagrams are actually gross simplifications of reality, and you have to do some quantum chemistry to really understand molecular structures. But you do need orbitals available to put in the extra electrons. And I think that symmetry is often a good guide also: were the F atoms able to gain extra electrons, that would result in a series of "ugly" resonance structures to account for all the possibilities.

 

[DeeNos]

I would recommend using the following steps to complete the Lewis structure for ClF4+:

1. Determine the central atom: In this case, the central atom is chlorine (Cl) because it is the least electronegative element.

2. Count the valence electrons: Chlorine has 7 valence electrons, and each fluorine atom has 7 valence electrons. Since there are 4 fluorine atoms, there are a total of 28 valence electrons in the molecule.

3. Add the positive charge: Since the molecule has a positive charge of +1, subtract one electron from the total number of valence electrons.

4. Place the atoms: Connect the central atom (Cl) to the surrounding atoms (F) using single bonds.

5. Distribute remaining electrons: Start by placing the remaining electrons on the outer atoms (F) to give them a full octet. In this case, each F atom will have 8 electrons (2 from the single bond and 6 from the remaining valence electrons).

6. Complete the octets on the central atom: After distributing the remaining electrons to the outer atoms, check to see if the central atom (Cl) has a complete octet. If it does not, move lone pairs from the outer atoms to form double or triple bonds with the central atom until it has a full octet.

7. Check formal charges: After completing the octets, check to see if any atoms have formal charges. If so, try to rearrange the electrons to minimize the formal charges.

In the case of ClF4+, the Lewis structure would look like this:

Cl
/ \
F F
/ \ / \
F F--F F
|
F

The total number of valence electrons used is 34, and the central atom (Cl) has a full octet. Each F atom also has a full octet, and there are no formal charges present.

I hope this helps you complete the Lewis structure for ClF4+. Remember to always follow the octet rule and check for formal charges to ensure a correct and stable structure.