Final answer:
Elements that are flammable, explosive, and present other hazards are labeled by the NFPA 704 Hazard Identification System, which uses a diamond-shaped label to indicate the level of hazard in terms of flammability, reactivity, health risks, and special characteristics like oxidizing properties.
Step-by-step explanation:
Elements that are flammable, explosive, and represent various other hazards are labeled according to the National Fire Protection Agency (NFPA) 704 Hazard Identification System. This system uses a diamond-shaped label to communicate safety information about substances. The NFPA 704 label includes a red diamond for flammability, a blue diamond for health risks, a yellow diamond for reactivity, and a white diamond for special hazards like oxidizers or corrosiveness. Each category is rated on a scale from 0 (no hazard) to 4 (extremely hazardous). For example, a substance that may detonate is given a 4 in the reactivity section, while an unstable material that can cause a violent chemical change is rated at 2 or 3 depending on the severity. Elements like potassium dichromate are oxidizers and can make other materials combust. Other examples include lithium-sulfur batteries and TNT explosives which fall under special hazards. It is critical to always follow specific instructions on handling flammable chemicals and recognize dangerous materials like the highly reactive nonmetal elements found in Group 7A (or 17) of the periodic table, also known as halogens.