Several technical names reveal information about atrazine structure. Each tells the same information but in slightly different form. The naming system used by Cornell University is: "6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine." Atrazine will be referred to as "2-chloro-4-(ethylamine)-6-(isopropylamine)-1,3,5-triazine". The reason for utilizing this "2-4-6-1,3,5" name is the more precise numeric designation (there is no potentially confusing "N..." portions). Numbers show where unique atoms and functional groups are located.
Numbers preceding each functional group refer to central ring locations. This molecular "core" is derived from the C6H6 benzene ring. Benzene is a structure with six carbon and six hydrogen atoms (hence the "C6H6") arranged in a circle. "Azine" refers to nitrogen replacing carbon atoms. Benzene and 1,3,5-triazine are often drawn as hexagons. Six hexagon corners correspond to the six carbon/nitrogen atoms.
Label the first nitrogen (at the "10-o-clock position" in the ChemSpider image) as "1" and count clockwise around the ring. The 1st, 3rd, and 5th hexagon corners are occupied by nitrogen atoms. If three nitrogen atoms replaced the carbon atoms in sequence instead of alternating with carbon, the ring would be called "1,2,3-triazine." If two nitrogen atoms were at opposite ends of the benzene ring, proper naming would be "1,4-diazine," and so on.
The "2-chloro" refers to chlorine atom position on the ring. Since nitrogen atoms are at ring-positions 1, 3, and 5, then position 2 on the ring is assumed to be occupied by a carbon atom. If any atom besides carbon is in the ring structure, details in the name (and image) would reveal this. From the name we know that atrazine has a chlorine atom bonded to the carbon in the 2nd vertex of the hexagon/ring.
Molecular structure images show two slightly different angled carbon-hydrogen "horns" or "sticks." These "sticks" are bonded to the central ring through a nitrogen (N) atom. The shorter "stick" is an ethylamine functional group. "Ethyl" refers to the "CH2-CH3" portion of the molecule. The "CH2" portion typically bonds to the rest of the molecule. "Amine" refers to a nitrogen-bonding structure. This nitrogen group ("NH") serves as a chemical link to the central 1,3,5-triazine ring.
Similarly, "isopropylamine" refers to the branched isopropyl carbon-hydrogen group. Once again, "amine" indicates a nitrogen atom that links to the central ring. Numbers preceding each name refer to the ring-atom each "-amine" functional group is bonded to. Ethylamine links to the fourth ring atom, isopropylamine bonds to the sixth. As with the "2-chloro" portion of the molecule, the ethylamine and isopropylamine bonding ring atoms are carbons.