
Victor K. answered 07/11/16
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Hi, Lara:
If we look up atrazine online, we get here https://en.wikipedia.org/wiki/Atrazine
This is what is called a "condensed" form that is commonly used in organic chemistry to draw larger molecules. Every angle symbolizes a carbon and hydrogens are generally omitted for the simplicity of drawing.
For and sp3 hybridized atom, we need to have 4 orbitals participating in the bonding AND making connections to 4 different other atoms. So, in this case, all carbons in the side chains will be sp3 hybridized (5 of them), likewise nitrogens have 3 bonds and an electron pair, which also occupies an orbital, so we can consider nitrogens in the side chains to also be connected to 4 things (so, 2 more nitrogens). Finally, the chlorine atom has one bond and 3 electron pairs sitting on it, so 4 things as well, so it is sp3 hybridized as well. In total, we have 5+2+1=8 sp3 hybridized atoms.
When it comes to sigma bonds--we have sigma bonds connecting all atoms, if the bond is double, it means that we have a sigma bond and a pi bond, for a triple bond, you have a sigma and two pi bonds. So, counting all "connections" in this molecule we'll get 28 sigma bonds if I didn't miss anything.
Hope that helps. Let me know if you have any questions.
Best,
Victor