If resources are being used faster than they are being replenished, then the species has exceeded its carrying capacity. If this occurs, the population will then decrease in size. Every stable population has one or more factors that limit its growth. A limiting factor determines the carrying capacity for a species.
Nitrogen, the next nonmetal, has 5 electrons in the valence shell, so it needs to combine with 3 hydrogen atoms to fulfill the octet rule and form a stable compound called ammonia (NH3).