In the valence bond picture of C2H2, each carbon atom is sp hybridized. This means that each carbon atom has two sp hybrid orbitals and two p orbitals. The two sp hybrid orbitals of each carbon atom overlap to form a sigma bond between the two carbon atoms. The two p orbitals of each carbon atom overlap with the p orbitals of the two hydrogen atoms to form two pi bonds, one between each carbon atom and each hydrogen atom.

The valence bond picture of C2H2 can be represented as follows:

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H-C≡C-H

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In this representation, the sigma bond between the two carbon atoms is represented by the solid line, and the two pi bonds between the carbon atoms and the hydrogen atoms are represented by the dashed lines.