Draw three Lewis structures for compounds with the formula \(\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{~F}_{2} .\) Indicate which of the compound(s) are polar.

Short Answer

Expert verified
The three possible Lewis structures for C2H2F2 can have the F and H either on the same C atom or on different ones, with all atoms having a formal charge of zero. Out of the three structures, only the one where each C atom is bonded to one H atom and one F atom results in a polar molecule, the other two are nonpolar as the dipoles cancel out.

Step by step solution

01

Identify the central atom

Identify the central atom in the molecule. In this case, there are two carbon atoms \(C\) and they are the central atoms.
02

Calculate valence electrons

Determine the total number of valence electrons. Carbon (C) has 4 valence electrons, Hydrogen (H) has 1 valence electron, and Fluorine (F) has 7 valence electrons. Hence, total valence electrons = 2*4(C) + 2*1(H) + 2*7(F) = 24 valence electrons.
03

Draw base structure

Draw a base structure that shows how the atoms are bonded.In the first structure, Carbon atoms are in the middle with two fluorines bonded to one carbon and two hydrogens bonded to the other carbon. In the second structure, each carbon is bonded to one hydrogen and one fluorine. In the third structure, there's alternating single and double bonds between carbon atoms, and each carbon atom is bonded to one hydrogen and one fluorine.
04

Draw Lone pairs

Place the remaining valence electrons as lone pairs on the atoms. Each fluorine atom will have 6 non-bonding electrons or 3 lone pairs after forming a bond.
05

Check formal charges

Check formal charges to ensure you have the best Lewis structure. Formal charge is the charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity. Each structure has a formal charge of zero, which is what we want for the most stable structure.
06

Determine polarity

A molecule is polar if the bond dipoles do not cancel each other out. In the first structure, the molecule is nonpolar as the bond dipoles cancel. In the second structure, the molecule is polar as the bond dipoles do not cancel. The third structure is nonpolar as the bond dipoles cancel.

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