Question

briefly explain how sp2 hybridised orbitals are formed. use diagrams to illustrate your answer. Clearly indicate the number, type and geometry of all orbitals involved

Answer 1

Question # 58854, Chemistry / Inorganic Chemistry | for completion

Briefly explain how sp2 hybridised orbitals are formed. use diagrams to illustrate your answer.

Clearly indicate the number, type and geometry of all orbitals involved

Answer

$\mathsf{sp}^2$ hybridization can explain the trigonal planar structure of molecules. In it, the 2s orbitals and two of the 2p orbitals hybridize to form three sp orbitals, each consisting of $67\%$ p and $33\%$ s character. The frontal lobes align themselves in the trigonal planar structure, pointing to the corners of a triangle in order to minimize electron repulsion and to improve overlap. The remaining p orbital remains unchanged and is perpendicular to the plane of the three $\mathsf{sp}^2$ orbitals.

Energy changes occurring in hybridization

Hybridization of an s orbital with two p orbitals $(\mathsf{p_x}$ and $\mathsf{p_y})$ results in three $\mathsf{sp}^2$ hybrid orbitals that are oriented at $120^{\circ}$ angle to each other. $\mathsf{Sp}^2$ hybridization results in trigonal geometry.

Example; $sp^2$ Hybridization in Aluminum Trihydride

In aluminum trihydride, one 2s orbital and two 2p orbitals hybridize to form three $\mathfrak{sp}^2$ orbitals that align themselves in the trigonal planar structure. The three Al $\mathfrak{sp}^2$ orbitals bond with with 1s orbitals from the three hydrogens through $\mathfrak{sp}^2$ -s orbital overlap.

Other molecules may be explained in a similar way. For example, ethene $(\mathrm{C}_2\mathrm{H}_4)$ has a double bond between the carbons.

Ethene structure

For this molecule, carbon $\mathfrak{sp}^2$ hybridises, because one $\pi$ (pi) bond is required for the double bond between the carbons and only three $\sigma$ bonds are formed per carbon atom. In $\mathfrak{sp}^2$ hybridisation the 2s orbital is mixed with only two of the three available 2p orbitals,

forming a total of three $\mathfrak{sp}^2$ orbitals with one remaining p orbital. In ethylene (ethene) the two carbon atoms form a $\sigma$ bond by overlapping two $\mathfrak{sp}^2$ orbitals and each carbon atom forms two covalent bonds with hydrogen by $s - \mathfrak{sp}^2$ overlap all with $120^\circ$ angles. The $\pi$ bond between the carbon atoms perpendicular to the molecular plane is formed by 2p-2p overlap. The hydrogen-carbon bonds are all of equal strength and length, in agreement with experimental data.

Three $\mathfrak{sp}^2$ orbitals.

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