Using the Lewis structure for the following hydrocarbon molecule, the carbons are numbered one to four...?

Question

starting with the far left carbon as one.

CH2CCHCH3

What is the molecular shape of carbon 3?

1. Bipyramidal

2. Square Planar

3. Trigonal Pyramidal

4. Tetrahedral

5. Linear

6. Trigonal Planar

7. Angular

Answer 1

Interesting molecule in that the second C atom is the midpoint of the two double bonds of the 'allene' structure. The molecule itself is methyl allene. The fourth C atom is tetrahedral in geometry. The CH2CCH portion is (almost) linear all by itself, but it makes up the fourth substituent group on the fourth C atom. The 3 H atoms are the other three substituents. All four substituents are arranged in a tetrahedral arrangement about the fourth C atom. You can visualize this as three balls and a hockey stick stuck to another ball.