In this exercise, molecular model kits will be used to give the student a better visual understanding of the three-dimensional nature and spatial relationships that occur in organic molecules. These ball and stick models are not accurate scale representations of the atom sizes and bond distances. They do, however, represent correct bond angles, and provide the student with a better visual picture of molecular structure than do the two-dimensional structural formulas usually used in textbooks. Models are of considerable help in understanding the nature of organic molecules and especially in visualizing structural differences that occur in isomers. The molecular model kit consists of atoms represented as enameled wooden or plastic balls drilled to receive connecting bonds. T

he number of holes corresponds to the number of covalent bonds which different atoms such as carbon, hydrogen, oxygen, etc. can form in producing organic molecules. The model atoms are colored to represent the different atoms commonly found in organic com- pounds. The main skeletal linkages (bonds) are represented by wood or plastic pegs. Follow the directions given in each part and answer the questions.. The carbon atom: 

a. Examine one of the carbon atom models. How many holes are found in the model? 

b. Insert a stick in each hole of the model carbon atom. What does each of these sticks гергesent? 

c. How many covalent bonds are necessary for each carbon atom in an organic molecule? 

d. Observe the bond angles represented by the sticks. Are all the bond angles the same?