SnCl2

[505934309]

Hello,

I am trying to make the lewis structure for SnCl2 and I have found a total of 18 valence electrons so I drew Sn in the middle with a Cl on either side and a double bond between one Sn and one Cl and filled in lone pairs everywhere else to complete the octet rule. However, when I googled the correct structure for this molecule it has a single bond between the Sn and each Cl and Sn had one lone pair. I know Sn doesn't follow the octet rule but I am confused because I feel like this usually manifests through expanding the octet. Can someone explain why this structure is the way that it is?

[Violet Webber 1F]

In this case, Sn and Cl would prefer to have a formal charge of 0. Sn has a value of 4 from the periodic table while Cl has a value of 7. You are correct about the 18 valence elections. If you drew one double bond to Cl and one single bond to Cl, Sn would have a formal charge of -1 (3 bonds and 2 lone atoms) while the Cl's would have a formal charge of 0. Since Cl is more electronegative, it would rather hold a negative charge than Sn, making this structure unstable.

If you give both Cl's a single bond to Sn, all three atoms will have a formal charge of 0. While Sn does not have a completed octet, it is happy because the compound as a whole has a charge of 0, and each atom has a charge of 0.