10. Lewis structure of C₄H₆.

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1. Calculate the total number of electrons in the valence shell of all the atoms in the molecule.

	Correct. The total number of valence shell electrons is 22.
	Wrong. Check the valence shell electrons of C and H atoms in the molecules.
	Wrong. Check the valence shell electrons of C and H atoms in the molecules.

2. Accepting that this molecule does not contain triple bonds between carbon atoms, and taking into account the H/C atoms ratio, find the number of double bonds in this molecule:

	Wrong. An hydrocarbon compound without double bonds should have a formula of type CnH2n+2. The formula for a saturated hydrocarbon compound with n=4 should be C4H10..
	Wrong. A four carbon atoms hydrocarbon should have formula C6H8.
	Correct. This compound has formula type CnH2n-2 corresponding to an unsaturated compound with two double bonds. Also would fit a compound with a triple C-C bond, but this possibility has been excluded in the introduction.

3. Choose the skeleton of the molecule:

	Wrong. In this skeleton a carbon atom is surrounded by three other carbon atoms. This skeleton cannot accommodate two double bonds.
	Correct. This compound has a linear skeleton of carbon atoms.
	Wrong. This skeleton is not in agreement with the formula of the selected compound

4. How many electrons are required to form all the C-H bonds?

	Wrong. Six C-H bonds require more than 10 electrons.
	Correct. Six C-H bonds require 12 electrons.
	Wrong. Six C-H bonds do not require as many as 14 electrons.

5. There are 4 electrons that have not been located. How do we locate these four electrons to complete the valence shell of all the carbon atoms?

One on each C atom.	Wrong. Such electron distribution would produce four radicals (carbon atoms with unpair electrons) that are not stable species.
Two on each terminal atom C1 and C4 .	Wrong In this case C2 and C3 do not complete the octeto.
Two double bonds between C1-C2 and C3-C4 atoms.	Correct All the atoms share eight electrons and the compound has a system of two conjugated doble bonds..

6. ¿How can we describe the geometry around each C atom??. Geometry

The four carbon atoms have a triangular planar geometry.	Correct. C1 and C4 sare bonded to one C atom and two hydrogens. C2 and C3 are bonded to two C atoms and one hydrogen. In both cases it is a AX3 environment. Triangular planar structure.
The four carbon atoms have a tetrahedral geometry.	Wrong. A tetrahedral geometry requires three atoms around each carbon atom. The carbon atoms have AX3 environment.

7. What hybridization can we assign to the C atoms?

All the C atom use sp2 orbitals	Correct. All have triangular planar geometry.
All the C atoms use sp3 orbitals	Wrong. Triangular planar geometry is not due to sp3 orbitals.