Question

Draw the orbital diagram for the hybridised carbons in ethene

QUESTION 52- WRITE YOUR ANSWER IN THE SPACE PROVIDED [5 marks] Each carbon in ethene (C2H4) is hybridised. a. Draw the Lewis diagram for ethene and indicate the hybridisation state for the carbons. [2 marks] b. Draw the orbital diagram for the hybridised carbons in ethene, clearly showing the hybrid carbon orbitals, as well as the electrons that they hold. [3 marks] For reference, the ground state orbitals for an unhybridised carbon have been included on the left. Hint: You need only consider what happens to the electrons in the n=2 orbitals in the hybridised state.

Answer 1

(a) Total valence electrons for C₂H₄ is 12.

It contains two carbon atoms that are double bonded to each other, with each of these atoms also bonded to two Hydrogen atoms.

C₂H₄ (named ethene) requires the use of a double bond. In a double bond two pairs of valence electrons are shared (for a total of four valence electrons).

н

C₂H₄ contains two carbon atoms that are double bonded to each other, with each of these atoms also bonded to two hydrogen atoms.

Total three bonds to each carbon atom, so its hybridization is sp² . Carbon atom is forming three sigma bonds instead of the four that it can, it only needs to hybridize three of its outer orbitals, instead of four.

By using the 2s electron and two of the 2p electrons, leaving the other unchanged. New orbital is called an sp² hybrid because it is made from one s orbital and two p orbitals.

(b) 2s orbital mixes with only two of the three available 2p orbitals, forming a total of three sp² orbitals with one p-orbital remaining.
The three hybridized orbitals explain the three sigma bonds that each carbon forms..

C" - Utill is sp2 sp2 sp27

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Molecular orbital diagram for ethene is given below:

中 Energ 。 | || 中中中中中 中 “H4 CH 1x CH: Atomic Orbital Ethene Molecular Orbital 1x CH2 Atomic Orbital