Question

what are the angles a and b in the actual molecule of which this is a lewis structure? note for advanced students: give the ideal angles, and dont worry about small differences from the ideal that might be caused by the fact that different electron groups may have slightly different sizes. a = ° b = °

Explanation:

Step1: Analyze carbon - carbon double - bonded carbon

The carbon with the double bond ($C = C$) has a trigonal - planar electron - pair geometry. The ideal bond angle for a trigonal - planar geometry is 120°. So, angle $a$ around the carbon - carbon double - bonded carbon is 120°.

Step2: Analyze the carbon - nitrogen single - bonded carbon

The carbon bonded to nitrogen ($C - N$) has a tetrahedral electron - pair geometry. The ideal bond angle for a tetrahedral geometry is 109.5°. So, angle $b$ around the carbon bonded to nitrogen is 109.5°.

Answer:

$a = 120$
$b = 109.5$