Problem 5 - Chemistry A Guided Inquiry

Question

Sketch a picture of the following molecules based on your models: \(\mathrm{CH}_{4} ; \mathrm{NH}_{3}\); \(\mathrm{H}_{2} \mathrm{O} .\)

Step-by-Step Solution

Answer

CH4 is a tetrahedral molecule, with Carbon in the center surrounded by Hydrogen atoms. NH3 is a pyramidal molecule, with Nitrogen at the peak and Hydrogen atoms at the corners. Finally, H2O is bent, with Oxygen in the center and Hydrogen atoms at the ends. Note the decreasing angles between atoms due to the increasing number of lone pairs.

Step 1: Draw CH4

Carbon in CH4 is the center atom and it has 4 Hydrogen atoms attached to it. There's no lone pair on the carbon atom. Hence, the shape of CH4 (methane) is tetrahedral. Carbon is in the center, with the Hydrogen atoms forming points around it at approximately 109.5 degrees apart.

Step 2: Draw NH3

In NH3, Nitrogen is the center atom and shares three bonds with three Hydrogen atoms. There is one lone pair on Nitrogen, which makes the molecule have a pyramidal shape. The nitrogen atom is at the peak of the pyramid, and the Hydrogen atoms are at the three bottom corners of the pyramid. The angles between bonds are about 107 degrees, slightly less than CH4 due to the presence of the lone pair.

Step 3: Draw H2O

Oxygen is the center atom in the H2O molecule, and there are two lone pairs of electrons and two bond pairs. This results in a bent shape. The Hydrogen atoms are at two corners and the lone electron pairs are at two other corners of a tetrahedron, making it a bent shape with an angle of approximately 104.5 degrees.