Lewis Dot Diagram

Question

Given the Lewis Dot Diagram for CH2F2 answer the following:

a) Only using the Lewis Dot Diagram can we tell if the C-H bond requires more energy to break (respond with either yes or no)?

b) Only using the Lewis Dot Diagram can we tel if the C-H bond length is longer or shorter than the C-F bond length (respond with either yes or no)?

Answer 1

C has 4 valence electrons, so 4 dots

F has 7 valence electrons and there are 2 F atoms, so 14 dots

H has 1 valence electron and there are two H atoms, so 2 dots

You have a total of 20 dots to place (4 + 14 + 2). Place them so every atom has a full valence orbital (8 for C and F and 2 for H):

JRS answered your questions about bond strength and length.

Answer 2

It isn't easy to draw Lewis structures on this platform, but you put the C in the middle, and bond it to 2 H atoms and 2 F atoms. The 2 F atoms will each have 3 lone pairs of electrons surrounding them. The molecular geometry will be tetrahedral and the C will be sp3 hybridized.

Because F is more electronegative than H, this will increase the p character of the C-F bond (and will decrease s character). This results in an increase in bond length of C-F bond. An increase in length leads to a weaker bond and so less energy would be needed to break this bond compared to the C-H bond.

So to answer (a), you might say yes, the C-H bond might require more energy to break

To answer (b), you might say yes, the C-H bond is shorter than the C-F bond.