Problem: The atoms of the compound methylhydrazine, CH6N2 which is used as a rocket propellant, are connected as follows:What do you predict for the ideal values of the C-N-N and H-N-H angles, respectively?

We can determine the electron geometry and bond angle using this:

Electron Regions          Electronic Geometry          Bond Angles

2                                      linear                                    180˚

3                                      trigonal planar                      120˚

4                                      tetrahedral                            109.5˚

5                                      trigonal bipyramidal              90˚, 120˚, and 180˚

6                                      octahedral                            90˚ and 180˚

Completing the given Lewis structure: 

• C prefers to form 4 bonds (Grp 4A)
• N prefers to form 3 bonds (Grp 5A)
  • add a lone pair to each N to satisfy octet rule (8 val. e^-)
• H forms only 1 bond (Grp 1A)

N (in C-N-N) is surrounded by:

• 4 electron groups: 3 bonds and 1 lone pair → tetrahedral