Question

Acetylene, C2H2 (also known as ethyne), is commonly used as a fuel for welding torches. Label each picture with the type of bond in acetylene that it describes. C-H sigma C-C sigma C-H pi C-C pi

Answer 1

Concepts and reason

The chemical bond is formed by the attraction of atom or ions. Due to electronegativity, the atoms can attract the electrons in the chemical bond. The chemical bonding is formed with the help of overlap of atomic orbitals.

There are two types of bonds. They are sigma bond $\left( \sigma \right)$ and pi bond $\left( {\rm{\pi }} \right)$ .

Fundamentals

Sigma bond:

The head – on overlapping of atomic orbitals which leads to a covalent bond formation is represented as sigma bond.

Pi bond:

A side wise overlapping of atomic orbitals which leads to the formation of bond is represented as pi bond.

Example:

The double bond in ethene contains 1 sigma bond and 1 pi bond. The 4 valance electrons of each carbon forms a bond with 2 hydrogen atom, 1 carbon – carbon sigma bond and 1carbon – carbon pi bond.

The double bond in ethene includes 1 ${\rm{\sigma }}\,{\rm{(s}}{{\rm{p}}^{\rm{2}}}{\rm{ - s}}{{\rm{p}}^{\rm{2}}}{\rm{ overlap)}}$ and 1 ${\rm{\pi }}\,{\rm{(p}}\,{\rm{ - }}\,{\rm{p overlap)}}$ bonds and each carbon – hydrogen bond shows ${\rm{\sigma }}\,{\rm{(s}}{{\rm{p}}^{\rm{2}}}{\rm{ - s overlap)}}$ .The bond angle is 120⁰ and shows Trigonal planar geometry.

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