Sp2 or sp3 hybrid orbitals

Sigma (o) bonds Bonds formed by the head-on overlap of sp, sp2, or sp3 hybrid orbitals with each other or with hydrogen 1s orbitals. 

The carbon atom with its 2s2, 2p2 electron configuration can form a maximum of four bonds which can be either single, double or triple. As a consequence as three main connectivities result depicted in Fig. 1. The valence orbitals hybridize forming, in the elemental state, sp, sp2 or sp3 hybrid orbitals. The data in Fig. 1 illustrate that the local bonding geometry and the carbon-carbon bond distances vary significantly with the connectivity as the bond order (and bond strength) increases from the sp3 to the sp hybridization state. 

Abstraction of an acetylenic proton gives a carbanion that has the lone pair of electrons in the sp hybrid orbital. Electrons in this orbital are close to the nucleus, and there is less charge separation than in carbanions with the lone pair in sp2 or sp3 hybrid orbitals. Ammonia and alcohols are included for comparison note that acetylene can be deprotonated by the amide ( NH2) ion, but not by an alkoxide ion ( OR). 

In such shorthand structures, each point where lines meet represents a carbon atom, and most H atoms are not shown. Draw the complete structure, showing all carbon and hydrogen atoms. (There will be four bonds to each carbon atom.) Indicate which carbon atoms use sp2 or sp3 hybrid orbitals. Are all carbon atoms in the same plane, as implied by the structure ... 

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