Question

5. What is the major difference between the two-dimensional and three- dimensional models of ethane and methane? When might you choose to use a two-dimensional model rather than a three-dimensional model when representing one of the molecules?

Answer 1

The major difference is that the two-dimensional model doesn't show the C-H angles. For example, three-dimensional models are needed to show stereo-isomerism

Answer 2

Two-dimensional structures of methane show that it is a carbon atom bonded to four (4) hydrogen atoms while ethane is two (2) carbon bound to six (6) hydrogens. The three-dimensional structures show that methane is tetrahedral is shape while ethane is trigonal pyramidal. The tw0-dimensional structure does not show bond angles and the position in space of the atoms within the molecule.

Two dimension structure can be used to illustrate a chemical reaction and the exchange of atoms by donors and acceptors in the reaction. Three-dimensional structures are significant in illustrating the crystal lattice of molecules since their 3-D structures determine how the molecules interact with each other.