Heteroatoms Halogens take the place of hydrogens,so add their number to the number of H's. Oxygen doesn't change the C:H ratio,so ignore oxygen in the formula. Nitrogen is trivalent,so it acts like half a carbon. HH H C-C-N C- 三> HHHH Chapter 7 9 Chapter 7 9 Heteroatoms • Halogens take the place of hydrogens, so add their number to the number of H’s. • Oxygen doesn’t change the C:H ratio, so ignore oxygen in the formula. • Nitrogen is trivalent, so it acts like half a carbon. C H H C H H N C H H H =>