Chapter 21.3, Problem 24SSC

Interpretation Introduction

Interpretation:

The geometric arrangement of the bonds around the carbon atoms in alkanes, alkenes, and alkynes needs to be determined.

Concept introduction:

The geometric shape of the molecule is predicted by VSEPR theory (Valence shell electron pair repulsion theory) from electron pairs surrounding the central atom of the molecule.

Answer to Problem 24SSC

According to VESPR the shape of the molecule:

Alkane is tetrahedral.

Alkene is trigonal planar.

Alkyne is linear.

Explanation of Solution

The geometric arrangement of the bonds around the carbon atoms in alkanes, alkenes, and alkynes are determined as:

• The structure of alkanes has single bond between carbon and hydrogen atoms. So, in alkane there is 4 bonded atoms and no lone pair across the carbon atom and thus, according to VESPR the shape of the molecule will be tetrahedral.



• The structure of alkenes has double bond between two carbon atoms. So, in alkene there is 3 bonded atoms and no lone pair across the carbon atom and thus, according to VESPR the shape of the molecule will be trigonal planar shape.



• The structure of alkynes has triple bond between two carbon atoms. So, in alkyne there is 2 bonded atoms and no lone pair across the carbon atom and thus, according to VESPR the shape of the molecule will be linear.